Bug 1482956 - Use an AutoTArray in PaintTask to reduce heap allocations. r=nical

There should only ever be at most four TextureClients here, so
allocated a vector seems wasteful.

--HG--
extra : rebase_source : 6b0f9f7749461eb39cd3c6c6bf7917152ffc9aab
extra : histedit_source : b5539d02c294596a5147dc55b417ef7970f8c0cd

gfx/layers/PaintThread.cpp

@@ -36,7 +36,7 @@ using namespace gfx;
 void
 PaintTask::DropTextureClients()
 {
-  mClients.clear();
+  mClients.Clear();
 }
 
 StaticAutoPtr<PaintThread> PaintThread::sSingleton;

gfx/layers/PaintThread.h

@@ -36,7 +36,7 @@ public:
 
   RefPtr<gfx::DrawTarget> mTarget;
   RefPtr<gfx::DrawTargetCapture> mCapture;
-  std::vector<RefPtr<TextureClient>> mClients;
+  AutoTArray<RefPtr<TextureClient>, 4> mClients;
 
 protected:
   virtual ~PaintTask() {}

gfx/layers/client/ContentClient.cpp

@@ -276,9 +276,9 @@ ContentClient::BeginPaint(PaintedLayer* aLayer,
 
   if (result.mAsyncPaint) {
     result.mAsyncTask->mTarget = mBuffer->GetBufferTarget();
-    result.mAsyncTask->mClients.push_back(mBuffer->GetClient());
+    result.mAsyncTask->mClients.AppendElement(mBuffer->GetClient());
     if (mBuffer->GetClientOnWhite()) {
-      result.mAsyncTask->mClients.push_back(mBuffer->GetClientOnWhite());
+      result.mAsyncTask->mClients.AppendElement(mBuffer->GetClientOnWhite());
     }
   }
 
@@ -887,9 +887,9 @@ ContentClientDoubleBuffered::FinalizeFrame(PaintState& aPaintState)
     mBuffer->UpdateDestinationFrom(*mFrontBuffer, updateRegion.GetBounds());
 
     if (aPaintState.mAsyncPaint) {
-      aPaintState.mAsyncTask->mClients.push_back(mFrontBuffer->GetClient());
+      aPaintState.mAsyncTask->mClients.AppendElement(mFrontBuffer->GetClient());
       if (mFrontBuffer->GetClientOnWhite()) {
-        aPaintState.mAsyncTask->mClients.push_back(mFrontBuffer->GetClientOnWhite());
+        aPaintState.mAsyncTask->mClients.AppendElement(mFrontBuffer->GetClientOnWhite());
       }
     }
 

gfx/layers/client/TiledContentClient.cpp

@@ -435,7 +435,7 @@ TileClient::ValidateFromFront(const nsIntRegion& aDirtyRegion,
                               gfx::DrawTarget* aBackBuffer,
                               TilePaintFlags aFlags,
                               IntRect* aCopiedRect,
-                              std::vector<RefPtr<TextureClient>>* aClients)
+                              AutoTArray<RefPtr<TextureClient>, 4>* aClients)
 {
   if (!mBackBuffer || !mFrontBuffer) {
     return;
@@ -479,9 +479,9 @@ TileClient::ValidateFromFront(const nsIntRegion& aDirtyRegion,
   aBackBuffer->CopySurface(frontSurface, rectToCopy, rectToCopy.TopLeft());
 
   if (aFlags & TilePaintFlags::Async) {
-    aClients->push_back(mFrontBuffer);
+    aClients->AppendElement(mFrontBuffer);
     if (mFrontBufferOnWhite) {
-      aClients->push_back(mFrontBufferOnWhite);
+      aClients->AppendElement(mFrontBufferOnWhite);
     }
   }
 
@@ -716,10 +716,10 @@ TileClient::AcquireBackBuffer(CompositableClient& aCompositable,
   }
 
   // Gather texture clients
-  std::vector<RefPtr<TextureClient>> clients;
-  clients.push_back(RefPtr<TextureClient>(mBackBuffer));
+  AutoTArray<RefPtr<TextureClient>, 4> clients;
+  clients.AppendElement(RefPtr<TextureClient>(mBackBuffer));
   if (mBackBufferOnWhite) {
-    clients.push_back(mBackBufferOnWhite);
+    clients.AppendElement(mBackBufferOnWhite);
   }
 
   // Copy from the front buerr to the back if necessary

gfx/layers/client/TiledContentClient.h

@@ -57,7 +57,7 @@ struct AcquiredBackBuffer
                      gfx::DrawTargetCapture* aCapture,
                      gfx::DrawTarget* aBackBuffer,
                      const gfx::IntRect& aUpdatedRect,
-                     std::vector<RefPtr<TextureClient>>&& aTextureClients)
+                     AutoTArray<RefPtr<TextureClient>, 4>&& aTextureClients)
     : mTarget(aTarget)
     , mCapture(aCapture)
     , mBackBuffer(aBackBuffer)
@@ -75,7 +75,7 @@ struct AcquiredBackBuffer
   RefPtr<gfx::DrawTargetCapture> mCapture;
   RefPtr<gfx::DrawTarget> mBackBuffer;
   gfx::IntRect mUpdatedRect;
-  std::vector<RefPtr<TextureClient>> mTextureClients;
+  AutoTArray<RefPtr<TextureClient>, 4> mTextureClients;
 };
 
 /**
@@ -204,7 +204,7 @@ private:
                          gfx::DrawTarget* aBackBuffer,
                          TilePaintFlags aFlags,
                          gfx::IntRect* aCopiedRegion,
-                         std::vector<RefPtr<TextureClient>>* aClients);
+                         AutoTArray<RefPtr<TextureClient>, 4>* aClients);
 };
 
 /**