--- a/gfx/layers/FrameMetrics.h
+++ b/gfx/layers/FrameMetrics.h
@@ -1099,14 +1099,23 @@ struct ZoomConstraints {
   }
 
   bool operator!=(const ZoomConstraints& other) const
   {
     return !(*this == other);
   }
 };
 
+struct ScrollableLayerGuidHash
+{
+  std::size_t operator()(const ScrollableLayerGuid& Guid) const
+  {
+    return Guid.Hash();
+  }
+};
+
+
 typedef Maybe<ZoomConstraints> MaybeZoomConstraints;
 
 } // namespace layers
 } // namespace mozilla
 
 #endif /* GFX_FRAMEMETRICS_H */

--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -81,17 +81,17 @@ struct APZCTreeManager::TreeBuildingStat
   // A list of nodes that need to be destroyed at the end of the tree building.
   // This is initialized with all nodes in the old tree, and nodes are removed
   // from it as we reuse them in the new tree.
   nsTArray<RefPtr<HitTestingTreeNode>> mNodesToDestroy;
 
   // This map is populated as we place APZCs into the new tree. Its purpose is
   // to facilitate re-using the same APZC for different layers that scroll
   // together (and thus have the same ScrollableLayerGuid).
-  std::map<ScrollableLayerGuid, AsyncPanZoomController*> mApzcMap;
+  std::unordered_map<ScrollableLayerGuid, AsyncPanZoomController*, ScrollableLayerGuidHash> mApzcMap;
 };
 
 class APZCTreeManager::CheckerboardFlushObserver : public nsIObserver {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSIOBSERVER
 
   explicit CheckerboardFlushObserver(APZCTreeManager* aTreeManager)
@@ -375,17 +375,17 @@ APZCTreeManager::PushStateToWR(wr::WebRe
 
   MutexAutoLock lock(mTreeLock);
 
   // During the first pass through the tree, we build a cache of guid->HTTN so
   // that we can find the relevant APZC instances quickly in subsequent passes,
   // such as the one below to generate scrollbar transforms. Without this, perf
   // could end up being O(n^2) instead of O(n log n) because we'd have to search
   // the tree to find the corresponding APZC every time we hit a thumb node.
-  std::map<ScrollableLayerGuid, HitTestingTreeNode*> httnMap;
+  std::unordered_map<ScrollableLayerGuid, HitTestingTreeNode*, ScrollableLayerGuidHash> httnMap;
 
   bool activeAnimations = false;
   uint64_t lastLayersId = -1;
   WrPipelineId lastPipelineId;
 
   // We iterate backwards here because the HitTestingTreeNode is optimized
   // for backwards iteration. The equivalent code in AsyncCompositionManager
   // iterates forwards, but the direction shouldn't really matter in practice
@@ -533,16 +533,18 @@ GetEventRegions(const ScrollNode& aLayer
     nsIntRegion hitRegion(compositionBounds.ToUnknownRect());
     EventRegions eventRegions(hitRegion);
     eventRegions.mDispatchToContentHitRegion = eventRegions.mHitRegion;
     return eventRegions;
   }
   return aLayer.GetEventRegions();
 }
 
+
+
 already_AddRefed<HitTestingTreeNode>
 APZCTreeManager::RecycleOrCreateNode(TreeBuildingState& aState,
                                      AsyncPanZoomController* aApzc,
                                      uint64_t aLayersId)
 {
   // Find a node without an APZC and return it. Note that unless the layer tree
   // actually changes, this loop should generally do an early-return on the
   // first iteration, so it should be cheap in the common case.

--- a/gfx/layers/apz/src/APZCTreeManager.h
+++ b/gfx/layers/apz/src/APZCTreeManager.h
@@ -1,17 +1,17 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef mozilla_layers_APZCTreeManager_h
 #define mozilla_layers_APZCTreeManager_h
 
-#include <map>                          // for std::map
+#include <unordered_map>                          // for std::unordered_map
 
 #include "gfxPoint.h"                   // for gfxPoint
 #include "mozilla/Assertions.h"         // for MOZ_ASSERT_HELPER2
 #include "mozilla/gfx/Logging.h"        // for gfx::TreeLog
 #include "mozilla/gfx/Matrix.h"         // for Matrix4x4
 #include "mozilla/layers/TouchCounter.h"// for TouchCounter
 #include "mozilla/layers/IAPZCTreeManager.h" // for IAPZCTreeManager
 #include "mozilla/Mutex.h"              // for Mutex
@@ -36,16 +36,17 @@ namespace layers {
 
 class Layer;
 class AsyncPanZoomController;
 class APZCTreeManagerParent;
 class CompositorBridgeParent;
 class OverscrollHandoffChain;
 struct OverscrollHandoffState;
 struct FlingHandoffState;
+struct ScrollableLayerGuidHash;
 class LayerMetricsWrapper;
 class InputQueue;
 class GeckoContentController;
 class HitTestingTreeNode;
 class WebRenderScrollData;
 
 /**
  * ****************** NOTE ON LOCK ORDERING IN APZ **************************
@@ -541,17 +542,17 @@ private:
    * lock also needs to be held when accessing the mRootNode instance variable, as that
    * is considered part of the APZC tree management state.
    * Finally, the lock needs to be held when accessing mZoomConstraints.
    * IMPORTANT: See the note about lock ordering at the top of this file. */
   mutable mozilla::Mutex mTreeLock;
   RefPtr<HitTestingTreeNode> mRootNode;
   /* Holds the zoom constraints for scrollable layers, as determined by the
    * the main-thread gecko code. */
-  std::map<ScrollableLayerGuid, ZoomConstraints> mZoomConstraints;
+  std::unordered_map<ScrollableLayerGuid, ZoomConstraints, ScrollableLayerGuidHash> mZoomConstraints;
   /* This tracks the APZC that should receive all inputs for the current input event block.
    * This allows touch points to move outside the thing they started on, but still have the
    * touch events delivered to the same initial APZC. This will only ever be touched on the
    * input delivery thread, and so does not require locking.
    */
   RefPtr<AsyncPanZoomController> mApzcForInputBlock;
   /* The hit result for the current input event block; this should always be in
    * sync with mApzcForInputBlock.