Slightly improve recovery from losing GL context.

mojo/skia/ganesh_context.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/skia/ganesh_context.h"
 
 #include "mojo/public/c/gpu/MGL/mgl.h"
 #include "mojo/skia/gl_bindings_skia.h"
 #include "third_party/skia/include/gpu/gl/GrGLInterface.h"
 
@@ skipping 28 matching lines @@
 }
 
 GaneshContext::~GaneshContext() {
   if (gl_context_)
     gl_context_->RemoveObserver(this);
 
   ReleaseContext();
 }
 
 void GaneshContext::OnContextLost() {
-  ReleaseContext();
+  context_lost_ = true;
+  if (!scope_entered_)
+    ReleaseContext();
 }
 
 void GaneshContext::ReleaseContext() {
   Scope(this);
   gr_context_->abandonContext();
   gr_context_.clear();
   gl_context_.reset();
 }
 
 void GaneshContext::EnterScope() {
   CHECK(!scope_entered_);
   scope_entered_ = true;
 
   if (gl_context_) {
     previous_mgl_context_ = MGLGetCurrentContext();
     gl_context_->MakeCurrent();
 
     // Reset the Ganesh context when entering its scope in case the caller
     // performed low-level GL operations which might interfere with Ganesh's
     // state expectations.
     if (gr_context_)
       gr_context_->resetContext();
   }
 }
 
 void GaneshContext::ExitScope() {
   CHECK(scope_entered_);
   scope_entered_ = false;
 
-  // Flush the Ganesh context when exiting its scope.
-  if (gr_context_)
-    gr_context_->flush();
+  if (gl_context_) {
+    // Flush the Ganesh context when exiting its scope.
+    if (gr_context_)
+      gr_context_->flush();
 
-  MGLMakeCurrent(previous_mgl_context_);
-  previous_mgl_context_ = MGL_NO_CONTEXT;
+    MGLMakeCurrent(previous_mgl_context_);
+    previous_mgl_context_ = MGL_NO_CONTEXT;
+
+    if (context_lost_)
+      ReleaseContext();
+  }
 }
 
 }  // namespace skia
 }  // namespace mojo