Updated the index buffer classes to use Error objects.

BUG=angle:520

Change-Id: Ifc249058a3ed3ffffe163a9e3ec21d6fc8c75bd0
Reviewed-on: https://chromium-review.googlesource.com/217101
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libGLESv2/Context.cpp b/src/libGLESv2/Context.cpp
index 985a756..aef626a 100644
--- a/src/libGLESv2/Context.cpp
+++ b/src/libGLESv2/Context.cpp
@@ -1788,16 +1788,16 @@
     VertexArray *vao = mState.getVertexArray();
     rx::TranslatedIndexData indexInfo;
     indexInfo.indexRange = indexRange;
-    GLenum err = mRenderer->applyIndexBuffer(indices, vao->getElementArrayBuffer(), count, mode, type, &indexInfo);
-    if (err != GL_NO_ERROR)
+    Error error = mRenderer->applyIndexBuffer(indices, vao->getElementArrayBuffer(), count, mode, type, &indexInfo);
+    if (error.isError())
     {
-        return gl::error(err);
+        return gl::error(error.getCode());
     }
 
     GLsizei vertexCount = indexInfo.indexRange.length() + 1;
-    err = mRenderer->applyVertexBuffer(programBinary, vao->getVertexAttributes(),
-                                       mState.getVertexAttribCurrentValues(),
-                                       indexInfo.indexRange.start, vertexCount, instances);
+    GLenum err = mRenderer->applyVertexBuffer(programBinary, vao->getVertexAttributes(),
+                                              mState.getVertexAttribCurrentValues(),
+                                              indexInfo.indexRange.start, vertexCount, instances);
     if (err != GL_NO_ERROR)
     {
         return gl::error(err);