Add an RAII class to lock and unlock textures. (bug 1222863 part 1, r=nical)

--HG--
extra : rebase_source : 730527b8495ea92a2d6fffc8bd6a6f97b2c3b6d3

gfx/layers/ImageContainer.cpp

@@ -650,12 +650,11 @@ CairoImage::GetTextureClient(CompositableClient *aClient)
     return nullptr;
   }
 
-  if (!textureClient->Lock(OpenMode::OPEN_WRITE_ONLY)) {
+  TextureClientAutoLock autoLock(textureClient, OpenMode::OPEN_WRITE_ONLY);
+  if (!autoLock.Succeeded()) {
     return nullptr;
   }
 
-  TextureClientAutoUnlock autoUnlock(textureClient);
-
   textureClient->UpdateFromSurface(surface);
 
   textureClient->SyncWithObject(forwarder->GetSyncObject());

gfx/layers/client/TextureClient.h

@@ -12,6 +12,7 @@
 #include "ImageTypes.h"                 // for StereoMode
 #include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc
 #include "mozilla/Attributes.h"         // for override
+#include "mozilla/DebugOnly.h"
 #include "mozilla/RefPtr.h"             // for RefPtr, RefCounted
 #include "mozilla/gfx/2D.h"             // for DrawTarget
 #include "mozilla/gfx/Point.h"          // for IntSize
@@ -720,17 +721,39 @@ protected:
   size_t mBufSize;
 };
 
-struct TextureClientAutoUnlock
+// Automatically lock and unlock a texture. Since texture locking is fallible,
+// Succeeded() must be checked on the guard object before proceeding.
+class MOZ_RAII TextureClientAutoLock
 {
-  TextureClient* mTexture;
+  MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER;
 
-  explicit TextureClientAutoUnlock(TextureClient* aTexture)
-  : mTexture(aTexture) {}
-
-  ~TextureClientAutoUnlock()
+public:
+  TextureClientAutoLock(TextureClient* aTexture, OpenMode aMode
+                        MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+   : mTexture(aTexture),
+     mSucceeded(false)
   {
-    mTexture->Unlock();
+    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+
+    mSucceeded = mTexture->Lock(aMode);
+    mChecked = false;
   }
+  ~TextureClientAutoLock() {
+    MOZ_ASSERT(mChecked);
+    if (mSucceeded) {
+      mTexture->Unlock();
+    }
+  }
+
+  bool Succeeded() {
+    mChecked = true;
+    return mSucceeded;
+  }
+
+private:
+  TextureClient* mTexture;
+  DebugOnly<bool> mChecked;
+  bool mSucceeded;
 };
 
 class KeepAlive

gfx/layers/ipc/SharedPlanarYCbCrImage.cpp

@@ -90,11 +90,13 @@ SharedPlanarYCbCrImage::SetData(const PlanarYCbCrData& aData)
   }
 
   MOZ_ASSERT(mTextureClient->AsTextureClientYCbCr());
-  if (!mTextureClient->Lock(OpenMode::OPEN_WRITE_ONLY)) {
+
+  TextureClientAutoLock autoLock(mTextureClient, OpenMode::OPEN_WRITE_ONLY);
+  if (!autoLock.Succeeded()) {
     MOZ_ASSERT(false, "Failed to lock the texture.");
     return false;
   }
-  TextureClientAutoUnlock unlock(mTextureClient);
+
   if (!mTextureClient->AsTextureClientYCbCr()->UpdateYCbCr(aData)) {
     MOZ_ASSERT(false, "Failed to copy YCbCr data into the TextureClient");
     return false;