command_buffer_gles2: Implement EGL default Display as a global object

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 ae331e5a4a080d4cf275e8cb35d2caf30011a28a..d23dbd9f5ea9c53204e7b941d6fc7b3558720feb 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -563,6 +563,7 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
   bool ResizeOffscreenFrameBuffer(const gfx::Size& size) override;
   void UpdateParentTextureInfo();
   bool MakeCurrent() override;
+  void ReleaseCurrent() override;
   GLES2Util* GetGLES2Util() override { return &util_; }
   gfx::GLContext* GetGLContext() override { return context_.get(); }
   ContextGroup* GetContextGroup() override { return group_.get(); }
@@ -3612,6 +3613,18 @@ bool GLES2DecoderImpl::MakeCurrent() {
   return true;
 }
 
+void GLES2DecoderImpl::ReleaseCurrent() {
+  if (!context_.get())
+    return;
+
+  if (WasContextLost()) {
+    LOG(ERROR) << "  GLES2DecoderImpl: Trying to release lost context.";
+    return;
+  }
+
+  context_->ReleaseCurrent(surface_.get());
+}
+
 void GLES2DecoderImpl::ProcessFinishedAsyncTransfers() {
   ProcessPendingReadPixels(false);
   if (engine() && query_manager_.get())
@@ -4133,7 +4146,7 @@ void GLES2DecoderImpl::Destroy(bool have_context) {
 void GLES2DecoderImpl::SetSurface(
     const scoped_refptr<gfx::GLSurface>& surface) {
   DCHECK(context_->IsCurrent(NULL));
-  DCHECK(surface_.get());
+  // Surface can be null, but then the client should not use the decoder.
   surface_ = surface;
   RestoreCurrentFramebufferBindings();
 }