WebGL: GL_RGB emulation for IOSurface backed textures. [For reference only]

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 7ecd8d5f47bf07b2f1410eb945e5d1295423c7b6..964aa05990b4b356537e0930c4e3ec6350bdcb52 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -683,6 +683,7 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
   // backbuffer if no framebuffer is bound.
   // Check with all attached and enabled color attachments.
   bool BoundFramebufferHasColorAttachmentWithAlpha();
+  bool BoundFramebufferEmulatingRGB();
   bool BoundFramebufferHasDepthAttachment();
   bool BoundFramebufferHasStencilAttachment();
 
@@ -4710,6 +4711,14 @@ bool GLES2DecoderImpl::BoundFramebufferHasColorAttachmentWithAlpha() {
   return BackBufferHasAlpha();
 }
 
+bool GLES2DecoderImpl::BoundFramebufferEmulatingRGB() {
+  Framebuffer* framebuffer =
+      GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER_EXT);
+  if (framebuffer)
+    return framebuffer->EmulatingRGB();
+  return false;
+}
+
 bool GLES2DecoderImpl::BoundFramebufferHasDepthAttachment() {
   Framebuffer* framebuffer =
       GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER_EXT);
@@ -4736,6 +4745,20 @@ bool GLES2DecoderImpl::BoundFramebufferHasStencilAttachment() {
 }
 
 void GLES2DecoderImpl::ApplyDirtyState() {
+  if (BoundFramebufferEmulatingRGB()) {
+    Framebuffer* framebuffer =
+        GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER_EXT);
+    if (framebuffer->HasUninitializedDrawBuffers()) {
+      glClearColor(0.2f, 0.2f, 0.2f, 1.0f);
+      state_.SetDeviceColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE);
+      glClear(GL_COLOR_BUFFER_BIT);
+      glClearColor(state_.color_clear_red, state_.color_clear_green,
+                   state_.color_clear_blue, state_.color_clear_alpha);
+      framebuffer->SetDrawBuffersAsInitialized();
+      framebuffer_state_.clear_state_dirty = true;
+    }
+  }
+
   if (framebuffer_state_.clear_state_dirty) {
     bool have_alpha = BoundFramebufferHasColorAttachmentWithAlpha();
     state_.SetDeviceColorMask(state_.color_mask_red,