Add debug option to clip each GrBatch to its device bounds

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index af62dafdd435787d610ecedc64d081214535b4f9..2861ae8ea230b44734fa54d238dbe9738b9580fb 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -806,12 +806,16 @@ int GPUSink::enclave() const {
 void PreAbandonGpuContextErrorHandler(SkError, void*) {}
 
 DEFINE_bool(imm, false, "Run gpu configs in immediate mode.");
+DEFINE_bool(batchClip, false, "Clip each GrBatch to its device bounds for testing.");
 
 Error GPUSink::draw(const Src& src, SkBitmap* dst, SkWStream*, SkString* log) const {
     GrContextOptions options;
     if (FLAGS_imm) {
         options.fImmediateMode = true;
     }
+    if (FLAGS_batchClip) {
+        options.fClipBatchToBounds = true;
+    }
     src.modifyGrContextOptions(&options);
 
     GrContextFactory factory(options);