Workaround for Intel 6xxx clear to 0/1 bug

ui/gl/gl_context.cc

 // Copyright (c) 2012 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 "ui/gl/gl_context.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/cancelable_callback.h"
@@ skipping 192 matching lines @@
   GLSurface::SetCurrent(surface);
   // Leave the real GL api current so that unit tests work correctly.
   // TODO(sievers): Remove this, but needs all gpu_unittest classes
   // to create and make current a context.
   if (!surface && GetGLImplementation() != kGLImplementationMockGL &&
       GetGLImplementation() != kGLImplementationStubGL) {
     SetCurrentGL(nullptr);
   }
 }
 
+GLWorkarounds GLContext::GetGLWorkarounds() {
+  return gl_workarounds_;
+}
+
+void GLContext::SetGLWorkarounds(const GLWorkarounds& workarounds) {
+  gl_workarounds_ = workarounds;
+}
+
 GLStateRestorer* GLContext::GetGLStateRestorer() {
   return state_restorer_.get();
 }
 
 void GLContext::SetGLStateRestorer(GLStateRestorer* state_restorer) {
   state_restorer_ = base::WrapUnique(state_restorer);
 }
 
 void GLContext::SetSwapInterval(int interval) {
   if (swap_interval_ == interval)
@@ skipping 13 matching lines @@
   return false;
 }
 
 void GLContext::InitializeDynamicBindings() {
   DCHECK(IsCurrent(nullptr));
   DCHECK(static_bindings_initialized_);
   if (!dynamic_bindings_initialized_) {
     if (real_gl_api_) {
       real_gl_api_->InitializeFilteredExtensions();
       real_gl_api_->set_version(GenerateGLVersionInfo());
+      real_gl_api_->setGLContext(this);

[Zhenyao Mo, 2017/06/26 21:45:22]

This is less optimal.  GLContext owns real_gl_api_, so you can easily pass
GLWorkaround to real_gl_api_ without creating this back link.

For example, in SetGLWorkarounds, you can just pass it to real_gl_api_.  If
real_gl_api_ is null at the time (please double check the life cycle and order
of things), then you can do it in GLContext::CreateGLApi()

[jiajia.qin, 2017/06/28 10:03:38]

Sorry for so many iterations. Please check the newest patch which will pass the
GLWorkarounds to RealGLApi. Beside that, patch set 9 is also a workable method.
Both are per-context and set GLWorkarounds by GLContext. The main differ is one
has GLWorkaround as a member of RealGLApi, another has GLWorkaround outside of
RealGLApi but in gl_gl_api_implementation.cc. If you think patch set 9 is more
simple, I can re-back to it. Thanks.

     }
 
     driver_gl_->InitializeDynamicBindings(GetVersionInfo(), GetExtensions());
     dynamic_bindings_initialized_ = true;
   }
 }
 
 bool GLContext::MakeVirtuallyCurrent(
     GLContext* virtual_context, GLSurface* surface) {
   if (!ForceGpuSwitchIfNeeded())
@@ skipping 83 matching lines @@
 
 scoped_refptr<GLContext> InitializeGLContext(scoped_refptr<GLContext> context,
                                              GLSurface* compatible_surface,
                                              const GLContextAttribs& attribs) {
   if (!context->Initialize(compatible_surface, attribs))
     return nullptr;
   return context;
 }
 
 }  // namespace gl