Update RenderbufferStorage EPs to new style.

This will facilitate changes for WebGL compatibility.

BUG=angleproject:747
BUG=angleproject:1708

Change-Id: I62e5d684ca10a843b5e958afe9954c1065bfeb19
Reviewed-on: https://chromium-review.googlesource.com/442093
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/Context.cpp b/src/libANGLE/Context.cpp
index 276a154..246ab66 100644
--- a/src/libANGLE/Context.cpp
+++ b/src/libANGLE/Context.cpp
@@ -3716,4 +3716,24 @@
     }
 }
 
+void Context::renderbufferStorage(GLenum target,
+                                  GLenum internalformat,
+                                  GLsizei width,
+                                  GLsizei height)
+{
+    Renderbuffer *renderbuffer = mGLState.getCurrentRenderbuffer();
+    handleError(renderbuffer->setStorage(internalformat, width, height));
+}
+
+void Context::renderbufferStorageMultisample(GLenum target,
+                                             GLsizei samples,
+                                             GLenum internalformat,
+                                             GLsizei width,
+                                             GLsizei height)
+{
+
+    Renderbuffer *renderbuffer = mGLState.getCurrentRenderbuffer();
+    handleError(renderbuffer->setStorageMultisample(samples, internalformat, width, height));
+}
+
 }  // namespace gl