Add option to control maximum GrBatch lookback

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 1c30d5427eb9bbcad6ea57f904d59a8499721c00..2b20e17ae16369155ba60ab6045f689db5f44341 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -89,6 +89,7 @@ void GrContext::initCommon(const GrContextOptions& options) {
     GrDrawTarget::Options dtOptions;
     dtOptions.fClipBatchToBounds = options.fClipBatchToBounds;
     dtOptions.fDrawBatchBounds = options.fDrawBatchBounds;
+    dtOptions.fMaxBatchLookback = options.fMaxBatchLookback;
     fDrawingManager.reset(new GrDrawingManager(this, dtOptions));
 
     // GrBatchFontCache will eventually replace GrFontCache