Get real GPU memory values on NV+Linux and OS X

ui/gl/gl_context.h

Index: ui/gl/gl_context.h
diff --git a/ui/gl/gl_context.h b/ui/gl/gl_context.h
index defeb25dc34f07e63ec4d40eb4005db2d2166420..7c0b669c0b3dcf1f80dd8269dfc9ad9d82e5484f 100644
--- a/ui/gl/gl_context.h
+++ b/ui/gl/gl_context.h
@@ -50,6 +50,11 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   // Returns space separated list of extensions. The context must be current.
   virtual std::string GetExtensions();
 
+  // Returns in bytes the total amount of GPU memory for the GPU which this
+  // context is currently rendering on. Returns false if no extension exists
+  // to get the exact amount of GPU memory.
+  virtual bool GetTotalGpuMemory(size_t* bytes);
+
   // Returns whether the current context supports the named extension. The
   // context must be current.
   bool HasExtension(const char* name);