Bug 784244: We really, seriously, can only let the BufferTracker take care of our required AutoOpenSurfaces. r=roc

gfx/layers/basic/BasicThebesLayer.cpp

@@ -259,6 +259,8 @@ struct NS_STACK_CLASS AutoBufferTracker {
     // they were constructed.
   }
 
+  gfxASurface* GetInitialBuffer() { return mInitialBuffer.ref().Get(); }
+
   gfxASurface*
   CreatedBuffer(const SurfaceDescriptor& aDescriptor) {
     Maybe<AutoOpenSurface>* surface = mNewBuffers.AppendElement();
@@ -267,7 +269,7 @@ struct NS_STACK_CLASS AutoBufferTracker {
   }
 
   Maybe<AutoOpenSurface> mInitialBuffer;
-  nsAutoTArray<Maybe<AutoOpenSurface>, 2> mNewBuffers;
+  nsAutoTArray<Maybe<AutoOpenSurface>, 3> mNewBuffers;
   BasicShadowableThebesLayer* mLayer;
 
 private:
@@ -328,20 +330,18 @@ BasicShadowableThebesLayer::SyncFrontBufferToBackBuffer()
   // that buffer when appropriate.
   MOZ_ASSERT(mBufferTracker);
 
-  gfxASurface* backBuffer = mBuffer.GetBuffer();
+  nsRefPtr<gfxASurface> backBuffer = mBuffer.GetBuffer();
   if (!IsSurfaceDescriptorValid(mBackBuffer)) {
     MOZ_ASSERT(!backBuffer);
     MOZ_ASSERT(mROFrontBuffer.type() == OptionalThebesBuffer::TThebesBuffer);
     const ThebesBuffer roFront = mROFrontBuffer.get_ThebesBuffer();
     AutoOpenSurface roFrontBuffer(OPEN_READ_ONLY, roFront.buffer());
-    AllocBackBuffer(roFrontBuffer.ContentType(), roFrontBuffer.Size());
+    backBuffer = CreateBuffer(roFrontBuffer.ContentType(), roFrontBuffer.Size());
   }
   mFrontAndBackBufferDiffer = false;
 
-  Maybe<AutoOpenSurface> autoBackBuffer;
   if (!backBuffer) {
-    autoBackBuffer.construct(OPEN_READ_WRITE, mBackBuffer);
-    backBuffer = autoBackBuffer.ref().Get();
+    backBuffer = mBufferTracker->GetInitialBuffer();
   }
 
   if (OptionalThebesBuffer::Tnull_t == mROFrontBuffer.type()) {
@@ -416,23 +416,6 @@ BasicShadowableThebesLayer::PaintBuffer(gfxContext* aContext,
                                       mBackBuffer);
 }
 
-void
-BasicShadowableThebesLayer::AllocBackBuffer(Buffer::ContentType aType,
-                                            const nsIntSize& aSize)
-{
-  // This function may *not* open the buffer it allocates.
-  if (!BasicManager()->AllocBuffer(gfxIntSize(aSize.width, aSize.height),
-                                   aType,
-                                   &mBackBuffer)) {
-    enum { buflen = 256 };
-    char buf[buflen];
-    PR_snprintf(buf, buflen,
-                "creating ThebesLayer 'back buffer' failed! width=%d, height=%d, type=%x",
-                aSize.width, aSize.height, int(aType));
-    NS_RUNTIMEABORT(buf);
-  }
-}
-
 already_AddRefed<gfxASurface>
 BasicShadowableThebesLayer::CreateBuffer(Buffer::ContentType aType,
                                          const nsIntSize& aSize)
@@ -451,7 +434,16 @@ BasicShadowableThebesLayer::CreateBuffer(Buffer::ContentType aType,
     mBackBuffer = SurfaceDescriptor();
   }
 
-  AllocBackBuffer(aType, aSize);
+  if (!BasicManager()->AllocBuffer(gfxIntSize(aSize.width, aSize.height),
+                                   aType,
+                                   &mBackBuffer)) {
+    enum { buflen = 256 };
+    char buf[buflen];
+    PR_snprintf(buf, buflen,
+                "creating ThebesLayer 'back buffer' failed! width=%d, height=%d, type=%x",
+                aSize.width, aSize.height, int(aType));
+    NS_RUNTIMEABORT(buf);
+  }
 
   NS_ABORT_IF_FALSE(!mIsNewBuffer,
                     "Bad! Did we create a buffer twice without painting?");

gfx/layers/basic/BasicThebesLayer.h

@@ -167,10 +167,6 @@ private:
               LayerManager::DrawThebesLayerCallback aCallback,
               void* aCallbackData) MOZ_OVERRIDE;
 
-  // This function may *not* open the buffer it allocates.
-  void
-  AllocBackBuffer(Buffer::ContentType aType, const nsIntSize& aSize);
-
   virtual already_AddRefed<gfxASurface>
   CreateBuffer(Buffer::ContentType aType, const nsIntSize& aSize) MOZ_OVERRIDE;