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 f28cc4387e7832e07bdf8335f303ff646fd0293c..a58c5e6d2b4f7524b1f53841fe3c4de7681db0f6 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -594,6 +594,7 @@ class GLES2DecoderImpl : public GLES2Decoder, public ErrorStateClient {
                   const std::vector<int32_t>& attribs) override;
   void Destroy(bool have_context) override;
   void SetSurface(const scoped_refptr<gfx::GLSurface>& surface) override;
+  void ReleaseSurface() override;
   void ProduceFrontBuffer(const Mailbox& mailbox) override;
   bool ResizeOffscreenFrameBuffer(const gfx::Size& size) override;
   void UpdateParentTextureInfo();
@@ -3683,6 +3684,7 @@ void GLES2DecoderImpl::DeleteSamplersHelper(
 // }  // anonymous namespace
 
 bool GLES2DecoderImpl::MakeCurrent() {
+  DCHECK(surface_);
   if (!context_.get())
     return false;
 
@@ -4240,11 +4242,22 @@ void GLES2DecoderImpl::Destroy(bool have_context) {
 void GLES2DecoderImpl::SetSurface(
     const scoped_refptr<gfx::GLSurface>& surface) {
   DCHECK(context_->IsCurrent(NULL));
-  DCHECK(surface_.get());
+  DCHECK(surface);
   surface_ = surface;
   RestoreCurrentFramebufferBindings();
 }
 
+void GLES2DecoderImpl::ReleaseSurface() {
+  if (!context_.get())
+    return;
+  if (WasContextLost()) {
+    DLOG(ERROR) << "  GLES2DecoderImpl: Trying to release lost context.";
+    return;
+  }
+  context_->ReleaseCurrent(surface_.get());
+  surface_ = nullptr;
+}
+
 void GLES2DecoderImpl::ProduceFrontBuffer(const Mailbox& mailbox) {
   if (!offscreen_saved_color_texture_.get()) {
     LOG(ERROR) << "Called ProduceFrontBuffer on a non-offscreen context";