Workaround for Intel 6xxx clear to 0/1 bug

ui/gl/gl_gl_api_implementation.cc

Index: ui/gl/gl_gl_api_implementation.cc
diff --git a/ui/gl/gl_gl_api_implementation.cc b/ui/gl/gl_gl_api_implementation.cc
index ecd5881e5c607a067e910a0ac23979c9be967a76..8a12fc6ab982d2aee78e4ec3c06d36436e962a8a 100644
--- a/ui/gl/gl_gl_api_implementation.cc
+++ b/ui/gl/gl_gl_api_implementation.cc
@@ -423,6 +423,21 @@ void RealGLApi::glClearFn(GLbitfield mask) {
     GLApiBase::glClearFn(mask);
 }
 
+void RealGLApi::glClearColorFn(GLclampf red,
+                               GLclampf green,
+                               GLclampf blue,
+                               GLclampf alpha) {
+  if (GLContext::GetGLWorkarounds().clear_to_zero_or_one_broken &&
+      (1 == red || 0 == red) && (1 == green || 0 == green) &&
+      (1 == blue || 0 == blue) && (1 == alpha || 0 == alpha)) {
+    if (1 == alpha)
+      alpha = 2;
+    else
+      alpha = -1;
+  }
+  GLApiBase::glClearColorFn(red, green, blue, alpha);
+}
+
 void RealGLApi::glDrawArraysFn(GLenum mode, GLint first, GLsizei count) {
   if (!g_null_draw_bindings_enabled)
     GLApiBase::glDrawArraysFn(mode, first, count);