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

src/gpu/GrDrawTargetCaps.h

Index: src/gpu/GrDrawTargetCaps.h
diff --git a/src/gpu/GrDrawTargetCaps.h b/src/gpu/GrDrawTargetCaps.h
index 61ec3b2196bba0f3077644cefe6456575a73e90c..9a08eff9df11b4efb67900d54d9d1680691bbced 100644
--- a/src/gpu/GrDrawTargetCaps.h
+++ b/src/gpu/GrDrawTargetCaps.h
@@ -80,7 +80,11 @@ public:
     bool pathRenderingSupport() const { return fPathRenderingSupport; }
     bool dstReadInShaderSupport() const { return fDstReadInShaderSupport; }
     bool discardRenderTargetSupport() const { return fDiscardRenderTargetSupport; }
+#if GR_FORCE_GPU_TRACE_DEBUGGING
+    bool gpuTracingSupport() const { return true; }
+#else
     bool gpuTracingSupport() const { return fGpuTracingSupport; }
+#endif
     bool compressedTexSubImageSupport() const { return fCompressedTexSubImageSupport; }
     bool oversizedStencilSupport() const { return fOversizedStencilSupport; }