Implementation of a GL-virtualization layer for Skia.  This allows for
environments using skia to specify a GL implementation at run-time, instead of
relying on the linker to pull in the appropriate GL impl.

A new structure, GrGLInterface is exposed.  This struct contains a set of
function pointers that should point to an appropriate GL implementation.

This change also removes the reliance on GLew on windows builds.

Review: http://codereview.appspot.com/4254059/



git-svn-id: http://skia.googlecode.com/svn/trunk@937 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrGLVertexBuffer.cpp b/gpu/src/GrGLVertexBuffer.cpp
index ec48936..69913bf 100644
--- a/gpu/src/GrGLVertexBuffer.cpp
+++ b/gpu/src/GrGLVertexBuffer.cpp
@@ -1,5 +1,5 @@
 /*
-    Copyright 2010 Google Inc.
+    Copyright 2011 Google Inc.
 
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
@@ -57,8 +57,7 @@
         // Let driver know it can discard the old data
         GR_GL(BufferData(GL_ARRAY_BUFFER, size(), NULL,
                          dynamic() ? GL_DYNAMIC_DRAW : GL_STATIC_DRAW));
-        fLockPtr = GR_GLEXT(fGL->extensions(),
-                            MapBuffer(GL_ARRAY_BUFFER, GR_WRITE_ONLY));
+        fLockPtr = GR_GL(MapBuffer(GL_ARRAY_BUFFER, GR_WRITE_ONLY));
         return fLockPtr;
     }
     return NULL;
@@ -74,7 +73,7 @@
     GrAssert(fGL->supportsBufferLocking());
 
     bind();
-    GR_GLEXT(fGL->extensions(), UnmapBuffer(GL_ARRAY_BUFFER));
+    GR_GL(UnmapBuffer(GL_ARRAY_BUFFER));
     fLockPtr = NULL;
 }