--- a/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js
+++ b/gfx/layers/apz/test/mochitest/apz_test_native_event_utils.js
@@ -112,24 +112,20 @@ function synthesizeNativeWheelAndWaitFor
   return synthesizeNativeWheel(aElement, aX, aY, aDeltaX, aDeltaY);
 }
 
 // Synthesizes a native mousewheel event and invokes the callback once the
 // first resulting scroll event is dispatched to |aElement|'s containing window.
 // If the event targets content in a subdocument, |aElement| should be inside
 // the subdocument.  See synthesizeNativeWheel for details on the other
 // parameters.
-var scrollActionId = 0;
 function synthesizeNativeWheelAndWaitForScrollEvent(aElement, aX, aY, aDeltaX, aDeltaY, aCallback) {
-  scrollActionId++;
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] initiating scroll action " + scrollActionId + "\n");
   var targetWindow = aElement.ownerDocument.defaultView;
   var useCapture = true;  // scroll events don't always bubble
   targetWindow.addEventListener("scroll", function scrollWaiter(e) {
-    dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scroll action " + scrollActionId + ": received scroll event, target is " + e.target + " with id " + e.target.id + "\n");
     targetWindow.removeEventListener("scroll", scrollWaiter, useCapture);
     setTimeout(aCallback, 0);
   }, useCapture);
   return synthesizeNativeWheel(aElement, aX, aY, aDeltaX, aDeltaY);
 }
 
 // Synthesizes a native mouse move event and returns immediately.
 // aX and aY are relative to the top-left of |aElement|'s containing window.

--- a/gfx/layers/apz/test/mochitest/test_wheel_transactions.html
+++ b/gfx/layers/apz/test/mochitest/test_wheel_transactions.html
@@ -40,98 +40,83 @@ https://bugzilla.mozilla.org/show_bug.cg
 </div>
 <pre id="test">
 <script type="application/javascript;version=1.7">
 
 function scrollWheelOver(element, deltaY) {
   synthesizeNativeWheelAndWaitForScrollEvent(element, 10, 10, 0, deltaY, driveTest);
 }
 
-function reportPositions(outer, inner) {
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] outer.scrollTop = " + outer.scrollTop + " and inner.scrollTop = " + inner.scrollTop + "\n");
-}
-
 function* runTest() {
   var outer = document.getElementById('outer-frame');
   var inner = document.getElementById('inner-frame');
   var innerContent = document.getElementById('inner-content');
 
   // Register a wheel event listener that records the target of
   // the last wheel event, so that we can make assertions about it.
   var lastWheelTarget;
   var wheelTargetRecorder = function(e) { lastWheelTarget = e.target; };
   window.addEventListener("wheel", wheelTargetRecorder);
 
   // Scroll |outer| to the bottom.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scrolling outer to the bottom\n");
   while (outer.scrollTop < outer.scrollTopMax) {
     yield scrollWheelOver(outer, -10);
-    reportPositions(outer, inner);
   }
 
   // Verify that this has brought |inner| under the wheel.
   is(lastWheelTarget, innerContent, "'inner-content' should have been brought under the wheel");
   window.removeEventListener("wheel", wheelTargetRecorder);
 
   // Immediately after, scroll it back up a bit.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scroll outer back up a bit\n");
   yield scrollWheelOver(outer, 10);
-  reportPositions(outer, inner);
 
   // Check that it was |outer| that scrolled back, and |inner| didn't
   // scroll at all, as all the above scrolls should be in the same
   // transaction.
   ok(outer.scrollTop < outer.scrollTopMax, "'outer' should have scrolled back a bit");
   is(inner.scrollTop, 0, "'inner' should not have scrolled");
 
   // The next part of the test is related to the transaction timeout.
   // Turn it down a bit so waiting for the timeout to elapse doesn't
   // slow down the test harness too much.
   var timeout = 5;
   yield SpecialPowers.pushPrefEnv({"set": [["mousewheel.transaction.timeout", timeout]]}, driveTest);
   SimpleTest.requestFlakyTimeout("we are testing code that measures actual elapsed time between two events");
 
   // Scroll up a bit more. It's still |outer| scrolling because
   // |inner| is still scrolled all the way to the top.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scrolling up\n");
   yield scrollWheelOver(outer, 10);
-  reportPositions(outer, inner);
 
   // Wait for the transaction timeout to elapse.
   // timeout * 5 is used to make it less likely that the timeout is less than
   // the system timestamp resolution
-  dump("[WHEEL_TRANS_LOG] waiting for timeout\n");
   yield window.setTimeout(driveTest, timeout * 5);
 
   // Now scroll down. The transaction having timed out, the event
   // should pick up a new target, and that should be |inner|.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scrolling down after waiting for timeout\n");
   yield scrollWheelOver(outer, -10);
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] checking if inner has scrolled\n");
   ok(inner.scrollTop > 0, "'inner' should have been scrolled");
 
   // Finally, test scroll handoff after a timeout.
 
   // Continue scrolling |inner| down to the bottom.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scrolling inner to the bottom\n");
   var prevScrollTop = inner.scrollTop;
   while (inner.scrollTop < inner.scrollTopMax) {
     yield scrollWheelOver(outer, -10);
     // Avoid a failure getting us into an infinite loop.
     ok(inner.scrollTop > prevScrollTop, "scrolling down should increase scrollTop");
     prevScrollTop = inner.scrollTop;
   }
 
   // Wait for the transaction timeout to elapse.
   // timeout * 5 is used to make it less likely that the timeout is less than
   // the system timestamp resolution
   yield window.setTimeout(driveTest, timeout * 5);
 
   // Continued downward scrolling should scroll |outer| to the bottom.
-  dump("[WHEEL_TRANS_LOG] [" + Date.now() + "] scrolling outer to the bottom\n");
   prevScrollTop = outer.scrollTop;
   while (outer.scrollTop < outer.scrollTopMax) {
     yield scrollWheelOver(outer, -10);
     // Avoid a failure getting us into an infinite loop.
     ok(outer.scrollTop > prevScrollTop, "scrolling down should increase scrollTop");
     prevScrollTop = outer.scrollTop;
   }
 }
@@ -150,19 +135,17 @@ function driveTest() {
 function startTest() {
   waitForAllPaints(function() {
     flushApzRepaints(driveTest);
   });
 }
 
 // Disable smooth scrolling because it makes the test flaky (we don't have a good
 // way of detecting when the scrolling is finished).
-SpecialPowers.pushPrefEnv({"set": [["general.smoothScroll", false],
-                                   ["layers.dump", true],
-                                   ["apz.printtree", true]]},
+SpecialPowers.pushPrefEnv({"set": [["general.smoothScroll", false]]},
                           function() {
                             SimpleTest.waitForFocus(startTest, window);
                           });
 
 SimpleTest.waitForExplicitFinish();
 
 </script>
 </pre>