Delay resize of the front buffer until the swap for offscreen buffers.

Previous code was resizing, and clearing the front buffer as soon as the back
buffer was resized. It can lead to race conditions where the compositor draws a
black texture if it triggers between the resize and the swap.

BUG=None
TEST=Pepper Flash


Review URL: http://codereview.chromium.org/7795015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98905 0039d316-1c4b-4281-b951-d872f2087c98

gpu/command_buffer/service/gles2_cmd_decoder.cc

@@ -2534,49 +2534,6 @@ bool GLES2DecoderImpl::ResizeOffscreenFrameBuffer(const gfx::Size& size) {
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
     RestoreClearState();
   }
-
-  // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
-  // crbug.com/94103. TODO(kbr): figure out reproduction so Apple will
-  // fix this.
-  if (needs_mac_nvidia_driver_workaround_) {
-    offscreen_saved_frame_buffer_->Create();
-    glFinish();
-  }
-
-  // Allocate the offscreen saved color texture.
-  DCHECK(offscreen_saved_color_format_);
-  offscreen_saved_color_texture_->AllocateStorage(
-      offscreen_size_, offscreen_saved_color_format_);
-
-  offscreen_saved_frame_buffer_->AttachRenderTexture(
-      offscreen_saved_color_texture_.get());
-  if (offscreen_saved_frame_buffer_->CheckStatus() !=
-      GL_FRAMEBUFFER_COMPLETE) {
-    LOG(ERROR) << "GLES2DecoderImpl::ResizeOffscreenFrameBuffer failed "
-               << "because offscreen saved FBO was incomplete.";
-    return false;
-  }
-
-  // Destroy the offscreen resolved framebuffers.
-  if (offscreen_resolved_frame_buffer_.get())
-    offscreen_resolved_frame_buffer_->Destroy();
-  if (offscreen_resolved_color_texture_.get())
-    offscreen_resolved_color_texture_->Destroy();
-  offscreen_resolved_color_texture_.reset();
-  offscreen_resolved_frame_buffer_.reset();
-
-  // Clear the offscreen color texture.
-  {
-    ScopedFrameBufferBinder binder(this, offscreen_saved_frame_buffer_->id());
-    glClearColor(0, 0, 0, 0);
-    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
-    glDisable(GL_SCISSOR_TEST);
-    glClear(GL_COLOR_BUFFER_BIT);
-    RestoreClearState();
-  }
-
-  UpdateParentTextureInfo();
-
   return true;
 }
 
@@ -6582,6 +6539,52 @@ error::Error GLES2DecoderImpl::HandleSwapBuffers(
   // If offscreen then don't actually SwapBuffers to the display. Just copy
   // the rendered frame to another frame buffer.
   if (is_offscreen) {
+    if (offscreen_size_ != offscreen_saved_color_texture_->size()) {
+      // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
+      // crbug.com/94163. TODO(kbr): figure out reproduction so Apple will
+      // fix this.
+      if (needs_mac_nvidia_driver_workaround_) {
+        offscreen_saved_frame_buffer_->Create();
+        glFinish();
+      }
+
+      // Allocate the offscreen saved color texture.
+      DCHECK(offscreen_saved_color_format_);
+      offscreen_saved_color_texture_->AllocateStorage(
+          offscreen_size_, offscreen_saved_color_format_);
+
+      offscreen_saved_frame_buffer_->AttachRenderTexture(
+          offscreen_saved_color_texture_.get());
+      if (offscreen_saved_frame_buffer_->CheckStatus() !=
+          GL_FRAMEBUFFER_COMPLETE) {
+        LOG(ERROR) << "GLES2DecoderImpl::ResizeOffscreenFrameBuffer failed "
+                   << "because offscreen saved FBO was incomplete.";
+        return error::kLostContext;
+      }
+
+      // Destroy the offscreen resolved framebuffers.
+      if (offscreen_resolved_frame_buffer_.get())
+        offscreen_resolved_frame_buffer_->Destroy();
+      if (offscreen_resolved_color_texture_.get())
+        offscreen_resolved_color_texture_->Destroy();
+      offscreen_resolved_color_texture_.reset();
+      offscreen_resolved_frame_buffer_.reset();
+
+      // Clear the offscreen color texture.
+      // TODO(piman): Is this still necessary?
+      {
+        ScopedFrameBufferBinder binder(this,
+                                       offscreen_saved_frame_buffer_->id());
+        glClearColor(0, 0, 0, 0);
+        glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+        glDisable(GL_SCISSOR_TEST);
+        glClear(GL_COLOR_BUFFER_BIT);
+        RestoreClearState();
+      }
+
+      UpdateParentTextureInfo();
+    }
+
     ScopedGLErrorSuppressor suppressor(this);
 
     if (IsOffscreenBufferMultisampled()) {