gpu: Support other buffer targets for ScopedBufferBinder

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 496068d0bc88846a638199415e4c4ef24c495176..064772e6b48e7fc94d66c020e7a1e01cd8ebc341 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -547,9 +547,6 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
   void RestoreActiveTextureUnitBinding(unsigned int target) const override {
     state_.RestoreActiveTextureUnitBinding(target);
   }
-  void RestoreBufferBinding(unsigned int target) const override {
-    state_.RestoreBufferBinding(target);
-  }
   void RestoreBufferBindings() const override {
     state_.RestoreBufferBindings();
   }
@@ -563,6 +560,7 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
   void RestoreVertexAttribArray(unsigned index) override {
     RestoreStateForAttrib(index, true);
   }
+  void RestoreBufferBinding(unsigned int target) override;
   void RestoreFramebufferBindings() const override;
   void RestoreRenderbufferBindings() override;
   void RestoreTextureState(unsigned service_id) const override;
@@ -5600,6 +5598,21 @@ void GLES2DecoderImpl::RestoreState(const ContextState* prev_state) {
   state_.RestoreState(prev_state);
 }
 
+void GLES2DecoderImpl::RestoreBufferBinding(unsigned int target) {
+  Buffer* bound_buffer =
+      buffer_manager()->GetBufferInfoForTarget(&state_, target);
+  if (target == GL_PIXEL_PACK_BUFFER) {
+    glPixelStorei(GL_PACK_ROW_LENGTH,

[piman, 2017/04/04 17:48:43]

We should only do these if we're on an ES3 context. Maybe you can use
state_.UpdatePackParameters() and state_.UpdateUnpackParameters().

[Chandan, 2017/04/04 18:18:45]

Thanks. As I see, these two methods are private. 
Will make these public?

[piman, 2017/04/04 19:59:14]

Alternatively, move this code to ContextState.

[Chandan, 2017/04/05 11:23:52]

The idea was to reuse BufferManager::GetBufferInfoForTarget instead of writing
similar code again to get bound buffer. However, it is not accessible from
ContextState. Therefore, I consciously did not move this code to ContextState to
avoid code duplication.
Another alternative I see is to pass BufferManager pointer to ContextState and
then access it there to get the buffer.
Making Update{Pack,UnPack}Parameters() public looks cleaner. WDYT?
I have uploaded patchset 2 which makes these 2 methods public in ContextState.
PTAL.

+                  bound_buffer ? state_.pack_row_length : 0);
+  } else if (target == GL_PIXEL_UNPACK_BUFFER) {
+    glPixelStorei(GL_UNPACK_ROW_LENGTH,
+                  bound_buffer ? state_.unpack_row_length : 0);
+    glPixelStorei(GL_UNPACK_IMAGE_HEIGHT,
+                  bound_buffer ? state_.unpack_image_height : 0);
+  }
+  glBindBuffer(target, bound_buffer ? bound_buffer->service_id() : 0);
+}
+
 void GLES2DecoderImpl::RestoreFramebufferBindings() const {
   GLuint service_id =
       framebuffer_state_.bound_draw_framebuffer.get()