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/GrGLTexture.cpp b/gpu/src/GrGLTexture.cpp
index 1acb871..7488d0f 100644
--- a/gpu/src/GrGLTexture.cpp
+++ b/gpu/src/GrGLTexture.cpp
@@ -43,16 +43,16 @@
     fGL->notifyRenderTargetDelete(this);
     if (fOwnIDs) {
         if (fTexFBOID) {
-            GR_GLEXT(fGL->extensions(), DeleteFramebuffers(1, &fTexFBOID));
+            GR_GL(DeleteFramebuffers(1, &fTexFBOID));
         }
         if (fRTFBOID && fRTFBOID != fTexFBOID) {
-            GR_GLEXT(fGL->extensions(), DeleteFramebuffers(1, &fRTFBOID));
+            GR_GL(DeleteFramebuffers(1, &fRTFBOID));
         }
         if (fStencilRenderbufferID) {
-            GR_GLEXT(fGL->extensions(), DeleteRenderbuffers(1, &fStencilRenderbufferID));
+            GR_GL(DeleteRenderbuffers(1, &fStencilRenderbufferID));
         }
         if (fMSColorRenderbufferID) {
-            GR_GLEXT(fGL->extensions(), DeleteRenderbuffers(1, &fMSColorRenderbufferID));
+            GR_GL(DeleteRenderbuffers(1, &fMSColorRenderbufferID));
         }
     }
     GrSafeUnref(fTexIDObj);