Only allocate the streaming index buffers when they are first needed.

BUG=angle:520

Change-Id: I111e4fd830ad19f6a4ff50749ba891fc14f9154b
Reviewed-on: https://chromium-review.googlesource.com/217100
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libGLESv2/renderer/d3d/IndexDataManager.h b/src/libGLESv2/renderer/d3d/IndexDataManager.h
index 93ec5ab..fef7f32 100644
--- a/src/libGLESv2/renderer/d3d/IndexDataManager.h
+++ b/src/libGLESv2/renderer/d3d/IndexDataManager.h
@@ -27,6 +27,7 @@
 
 namespace rx
 {
+class IndexBufferInterface;
 class StaticIndexBufferInterface;
 class StreamingIndexBufferInterface;
 class IndexBuffer;
@@ -54,6 +55,8 @@
     GLenum prepareIndexData(GLenum type, GLsizei count, gl::Buffer *arrayElementBuffer, const GLvoid *indices, TranslatedIndexData *translated);
 
   private:
+    GLenum getStreamingIndexBuffer(GLenum destinationIndexType, IndexBufferInterface **outBuffer);
+
     DISALLOW_COPY_AND_ASSIGN(IndexDataManager);
 
     Renderer *const mRenderer;