Added switch to disable specified GL extensions.

ui/gl/gl_gl_api_implementation.h

Index: ui/gl/gl_gl_api_implementation.h
diff --git a/ui/gl/gl_gl_api_implementation.h b/ui/gl/gl_gl_api_implementation.h
index d4086006b6b51babf299646b6c7594d2fb06ccef..9594bfde917002b1dda3da24ad5eeab5b256ccab 100644
--- a/ui/gl/gl_gl_api_implementation.h
+++ b/ui/gl/gl_gl_api_implementation.h
@@ -5,10 +5,15 @@
 #ifndef UI_GL_GL_GL_API_IMPLEMENTATION_H_
 #define UI_GL_GL_GL_API_IMPLEMENTATION_H_
 
+#include <vector>
+
 #include "base/compiler_specific.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_export.h"
 
+namespace base {
+class CommandLine;
+}
 namespace gpu {
 namespace gles2 {
 class GLES2Decoder;
@@ -54,10 +59,20 @@ class RealGLApi : public GLApiBase {
   RealGLApi();
   ~RealGLApi() override;
   void Initialize(DriverGL* driver);
+  void InitializeWithCommandLine(DriverGL* driver,
+                                 base::CommandLine* command_line);

[no sievers, 2015/05/01 21:55:00]

So somebody has to call this in the production code for it to work.
That being said, don't you rather want to just add this argument to
Initialize()?

[David Yen, 2015/05/01 22:34:38]

In Initialize() it defaults to using the process command line arguments. It was
pointed out by zmo that adding default parameters is against the style guide, so
I followed how gl_manager had added a command_line parameter.

[no sievers, 2015/05/01 22:48:35]

My bad. I missed that Initialize() calls this with
CommandLine::ForCurrentProcess().
So this method should be called InitializeForTesting().

[David Yen, 2015/05/01 22:59:35]

I actually prefer the more descriptive name, but how about we meet in the middle
and I just change the name to an overloaded Initialize with a CommandLine
parameter.

+
+  void glGetIntegervFn(GLenum pname, GLint* params) override;
+  const GLubyte* glGetStringFn(GLenum name) override;
+  const GLubyte* glGetStringiFn(GLenum name, GLuint index) override;
 
  private:
   void glFinishFn() override;
   void glFlushFn() override;
+
+  // Filtered GL_EXTENSIONS we return to glGetString(i) calls.
+  std::vector<std::string> filtered_exts_;
+  std::string filtered_exts_str_;
 };
 
 // Inserts a TRACE for every GL call.