Add flag to force gpu trace markers to be used and printed out for debugging.

include/gpu/GrConfig.h

Index: include/gpu/GrConfig.h
diff --git a/include/gpu/GrConfig.h b/include/gpu/GrConfig.h
index d48ccd5dc6ff5de1d0a8d05d30c7a35c009afe80..6a00eabe146f3aab1c6bff34fa8850d673ba4b0a 100644
--- a/include/gpu/GrConfig.h
+++ b/include/gpu/GrConfig.h
@@ -232,4 +232,12 @@ typedef unsigned __int64 uint64_t;
     #define GR_ALWAYS_ALLOCATE_ON_HEAP 0
 #endif
 
+/**
+ * GR_FORCE_GPU_TRACE_DEBUGGING will force gpu tracing/debug markers to be turned on. The trace
+ * markers will be printed out instead of making the backend calls to push and pop them.
+ */
+#if !defined(GR_FORCE_GPU_TRACE_DEBUGGING)
+    #define GR_FORCE_GPU_TRACE_DEBUGGING 0
+#endif
+
 #endif