Fix glDrawRangeElements

Adds explicit min/max index value fields to GrMesh. This eliminates the
previous assumption that the index values were within the range
[0..vertexCount-1]. In the pattern case we still maintain this
assumption.

Updates GrMesh to hide its fields and handle its new complexity using a
"helper" interface instead.

Adds a unit test for GrMesh.

Bug: skia:
Change-Id: Ia23de72d510f8827cee56072b727fb70a6e46b8d
Reviewed-on: https://skia-review.googlesource.com/17964
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/ops/GrNonAAStrokeRectOp.cpp b/src/gpu/ops/GrNonAAStrokeRectOp.cpp
index 4e00847..f386984 100644
--- a/src/gpu/ops/GrNonAAStrokeRectOp.cpp
+++ b/src/gpu/ops/GrNonAAStrokeRectOp.cpp
@@ -157,7 +157,8 @@
         }
 
         GrMesh mesh(primType);
-        mesh.setVertices(vertexBuffer, vertexCount, firstVertex);
+        mesh.setNonIndexed(vertexCount);
+        mesh.setVertexData(vertexBuffer, firstVertex);
         target->draw(gp.get(), this->pipeline(), mesh);
     }