Fix ANGLE build wrong glGetString being called issue

src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp

Index: src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp
diff --git a/src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp b/src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp
index d63dfbbcd63edf3bd6cd9f3f8f1f5a884e930f0a..7afa2e07625999930d161be0eb98a6edcf47d034 100644
--- a/src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp
+++ b/src/gpu/gl/win/GrGLCreateNativeInterface_win.cpp
@@ -82,7 +82,11 @@ const GrGLInterface* GrGLCreateNativeInterface() {
         return NULL;
     }
 
-    const char* verStr = reinterpret_cast<const char*>(glGetString(GR_GL_VERSION));
+    GrGLGetStringProc getString = (GrGLGetStringProc)getter.getProc("glGetString");
+    if (NULL == getString) {
+        return NULL;
+    }
+    const char* verStr = reinterpret_cast<const char*>(getString(GR_GL_VERSION));
     GrGLStandard standard = GrGLGetStandardInUseFromString(verStr);
 
     if (kGLES_GrGLStandard == standard) {