--- a/devtools/client/shared/test/browser_html_tooltip-01.js
+++ b/devtools/client/shared/test/browser_html_tooltip-01.js
@@ -35,17 +35,17 @@ function getTooltipContent(doc) {
 
 add_task(function* () {
   yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   let tooltip = new HTMLTooltip({doc}, {});
 
   info("Set tooltip content");
-  yield tooltip.setContent(getTooltipContent(doc), 100, 50);
+  tooltip.setContent(getTooltipContent(doc), 100, 50);
 
   is(tooltip.isVisible(), false, "Tooltip is not visible");
 
   info("Show the tooltip and check the expected events are fired.");
 
   let shown = 0;
   tooltip.on("shown", () => shown++);
 

--- a/devtools/client/shared/test/browser_html_tooltip-02.js
+++ b/devtools/client/shared/test/browser_html_tooltip-02.js
@@ -37,33 +37,33 @@ add_task(function* () {
   yield testClickInOuterIframe(doc);
   yield testClickInInnerIframe(doc);
 });
 
 function* testClickInTooltipContent(doc) {
   info("Test a tooltip is not closed when clicking inside itself");
 
   let tooltip = new HTMLTooltip({doc}, {});
-  yield tooltip.setContent(getTooltipContent(doc), 100, 50);
+  tooltip.setContent(getTooltipContent(doc), 100, 50);
   yield showTooltip(tooltip, doc.getElementById("box1"));
 
   let onTooltipContainerClick = once(tooltip.container, "click");
   EventUtils.synthesizeMouseAtCenter(tooltip.container, {}, doc.defaultView);
   yield onTooltipContainerClick;
   is(tooltip.isVisible(), true, "Tooltip is still visible");
 
   tooltip.destroy();
 }
 
 function* testConsumeOutsideClicksFalse(doc) {
   info("Test closing a tooltip via click with consumeOutsideClicks: false");
   let box4 = doc.getElementById("box4");
 
   let tooltip = new HTMLTooltip({doc}, {consumeOutsideClicks: false});
-  yield tooltip.setContent(getTooltipContent(doc), 100, 50);
+  tooltip.setContent(getTooltipContent(doc), 100, 50);
   yield showTooltip(tooltip, doc.getElementById("box1"));
 
   let onBox4Clicked = once(box4, "click");
   let onHidden = once(tooltip, "hidden");
   EventUtils.synthesizeMouseAtCenter(box4, {}, doc.defaultView);
   yield onHidden;
   yield onBox4Clicked;
 
@@ -76,17 +76,17 @@ function* testConsumeOutsideClicksTrue(d
   info("Test closing a tooltip via click with consumeOutsideClicks: true");
   let box4 = doc.getElementById("box4");
 
   // Count clicks on box4
   let box4clicks = 0;
   box4.addEventListener("click", () => box4clicks++);
 
   let tooltip = new HTMLTooltip({doc}, {consumeOutsideClicks: true});
-  yield tooltip.setContent(getTooltipContent(doc), 100, 50);
+  tooltip.setContent(getTooltipContent(doc), 100, 50);
   yield showTooltip(tooltip, doc.getElementById("box1"));
 
   let onHidden = once(tooltip, "hidden");
   EventUtils.synthesizeMouseAtCenter(box4, {}, doc.defaultView);
   yield onHidden;
 
   is(box4clicks, 0, "box4 catched no click event");
   is(tooltip.isVisible(), false, "Tooltip is hidden");
@@ -94,17 +94,17 @@ function* testConsumeOutsideClicksTrue(d
   tooltip.destroy();
 }
 
 function* testClickInOuterIframe(doc) {
   info("Test clicking an iframe outside of the tooltip closes the tooltip");
   let frame = doc.getElementById("frame");
 
   let tooltip = new HTMLTooltip({doc});
-  yield tooltip.setContent(getTooltipContent(doc), 100, 50);
+  tooltip.setContent(getTooltipContent(doc), 100, 50);
   yield showTooltip(tooltip, doc.getElementById("box1"));
 
   let onHidden = once(tooltip, "hidden");
   EventUtils.synthesizeMouseAtCenter(frame, {}, doc.defaultView);
   yield onHidden;
 
   is(tooltip.isVisible(), false, "Tooltip is hidden");
   tooltip.destroy();
@@ -113,17 +113,17 @@ function* testClickInOuterIframe(doc) {
 function* testClickInInnerIframe(doc) {
   info("Test clicking an iframe inside the tooltip content does not close the tooltip");
 
   let tooltip = new HTMLTooltip({doc}, {consumeOutsideClicks: false});
 
   let iframe = doc.createElementNS(HTML_NS, "iframe");
   iframe.style.width = "100px";
   iframe.style.height = "50px";
-  yield tooltip.setContent(iframe, 100, 50);
+  tooltip.setContent(iframe, 100, 50);
   yield showTooltip(tooltip, doc.getElementById("box1"));
 
   let onTooltipContainerClick = once(tooltip.container, "click");
   EventUtils.synthesizeMouseAtCenter(tooltip.container, {}, doc.defaultView);
   yield onTooltipContainerClick;
 
   is(tooltip.isVisible(), true, "Tooltip is still visible");
 

--- a/devtools/client/shared/test/browser_html_tooltip-03.js
+++ b/devtools/client/shared/test/browser_html_tooltip-03.js
@@ -127,11 +127,11 @@ function blurNode(doc, selector) {
  */
 function* createTooltip(doc, autofocus) {
   let tooltip = new HTMLTooltip({doc}, {autofocus});
   let div = doc.createElementNS(HTML_NS, "div");
   div.classList.add("tooltip-content");
   div.style.height = "50px";
   div.innerHTML = '<input type="text"></input>';
 
-  yield tooltip.setContent(div, 150, 50);
+  tooltip.setContent(div, 150, 50);
   return tooltip;
 }

--- a/devtools/client/shared/test/browser_html_tooltip-04.js
+++ b/devtools/client/shared/test/browser_html_tooltip-04.js
@@ -38,17 +38,17 @@ add_task(function* () {
 
   yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "100%";
-  yield tooltip.setContent(div, TOOLTIP_WIDTH, TOOLTIP_HEIGHT);
+  tooltip.setContent(div, TOOLTIP_WIDTH, TOOLTIP_HEIGHT);
 
   let box1 = doc.getElementById("box1");
   let box2 = doc.getElementById("box2");
   let box3 = doc.getElementById("box3");
   let box4 = doc.getElementById("box4");
   let height = TOOLTIP_HEIGHT, width = TOOLTIP_WIDTH;
 
   // box1: Can only fit below box1

--- a/devtools/client/shared/test/browser_html_tooltip-05.js
+++ b/devtools/client/shared/test/browser_html_tooltip-05.js
@@ -35,17 +35,17 @@ add_task(function* () {
 
   yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "100%";
-  yield tooltip.setContent(div, TOOLTIP_WIDTH, TOOLTIP_HEIGHT);
+  tooltip.setContent(div, TOOLTIP_WIDTH, TOOLTIP_HEIGHT);
 
   let box1 = doc.getElementById("box1");
   let box2 = doc.getElementById("box2");
   let box3 = doc.getElementById("box3");
   let box4 = doc.getElementById("box4");
   let width = TOOLTIP_WIDTH;
 
   // box1: Can not fit above or below box1, default to bottom with a reduced

--- a/devtools/client/shared/test/browser_html_tooltip_arrow-01.js
+++ b/devtools/client/shared/test/browser_html_tooltip_arrow-01.js
@@ -55,17 +55,17 @@ add_task(function* () {
 
   yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {type: "arrow"});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "35px";
-  yield tooltip.setContent(div, 200, 35);
+  tooltip.setContent(div, 200, 35);
 
   let {right: docRight} = doc.documentElement.getBoundingClientRect();
 
   let elements = [...doc.querySelectorAll(".anchor")];
   for (let el of elements) {
     info("Display the tooltip on an anchor.");
     yield showTooltip(tooltip, el);
 

--- a/devtools/client/shared/test/browser_html_tooltip_arrow-02.js
+++ b/devtools/client/shared/test/browser_html_tooltip_arrow-02.js
@@ -49,17 +49,17 @@ add_task(function* () {
 
   yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {type: "arrow"});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "35px";
-  yield tooltip.setContent(div, 200, 35);
+  tooltip.setContent(div, 200, 35);
 
   let {right: docRight} = doc.documentElement.getBoundingClientRect();
 
   let elements = [...doc.querySelectorAll(".anchor")];
   for (let el of elements) {
     info("Display the tooltip on an anchor.");
     yield showTooltip(tooltip, el);
 

--- a/devtools/client/shared/widgets/HTMLTooltip.js
+++ b/devtools/client/shared/widgets/HTMLTooltip.js
@@ -110,18 +110,16 @@ HTMLTooltip.prototype = {
    *        The tooltip content, should be a HTML element.
    * @param {Number} width
    *        Preferred width for the tooltip container
    * @param {Number} height (optional)
    *        Preferred height for the tooltip container. If the content height is
    *        smaller than the container's height, the tooltip will automatically
    *        shrink around the content. If not specified, will use all the height
    *        available.
-   * @return {Promise} a promise that will resolve when the content has been
-   *         added in the tooltip container.
    */
   setContent: function (content, width, height = Infinity) {
     let themeHeight = EXTRA_HEIGHT[this.type] + 2 * EXTRA_BORDER[this.type];
     let themeWidth = 2 * EXTRA_BORDER[this.type];
 
     this.preferredWidth = width + themeWidth;
     this.preferredHeight = height + themeHeight;