Support ES 3.0 constants for bufferData's usage argument.

Source/modules/webgl/WebGLRenderingContextBase.h

Index: Source/modules/webgl/WebGLRenderingContextBase.h
diff --git a/Source/modules/webgl/WebGLRenderingContextBase.h b/Source/modules/webgl/WebGLRenderingContextBase.h
index c6cb76eacb089a3c6ce423667f5ee65a41410ce6..3a4a618cf7d700c9130f2e281adffccdb21da2ec 100644
--- a/Source/modules/webgl/WebGLRenderingContextBase.h
+++ b/Source/modules/webgl/WebGLRenderingContextBase.h
@@ -969,6 +969,8 @@ protected:
     // Helper function to validate the target for bufferData.
     // Return the current bound buffer to target, or 0 if the target is invalid.
     virtual WebGLBuffer* validateBufferDataTarget(const char* functionName, GLenum target);
+    // Helper function to validate the usage for bufferData.
+    virtual bool validateBufferDataUsage(const char* functionName, GLenum usage);
 
     virtual bool validateAndUpdateBufferBindTarget(const char* functionName, GLenum target, WebGLBuffer*);