Add the ability to enable/disable GPU path renderers

Adds a bitfield to GrContextOptions that masks out path renderers.
Adds commandline flags support to set this bitfield in tools apps.
Removes GrGLInterfaceRemoveNVPR since we can now accomplish the same
thing in the context options.

BUG=skia:

Change-Id: Icf2a4df36374b3ba2f69ebf0db56e8aedd6cf65f
Reviewed-on: https://skia-review.googlesource.com/8786
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index e97e9a0..f73ae46 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -33,6 +33,7 @@
 #include "SkCodec.h"
 #include "SkCommonFlags.h"
 #include "SkCommonFlagsConfig.h"
+#include "SkCommonFlagsPathRenderer.h"
 #include "SkData.h"
 #include "SkGraphics.h"
 #include "SkLeanWindows.h"
@@ -128,6 +129,10 @@
 DEFINE_string(benchType,  "",
         "Apply usual --match rules to bench type: micro, recording, piping, playback, skcodec, etc.");
 
+#if SK_SUPPORT_GPU
+DEFINE_pathrenderer_flag;
+#endif
+
 static double now_ms() { return SkTime::GetNSecs() * 1e-6; }
 
 static SkString humanize(double ms) {
@@ -1106,6 +1111,7 @@
 
 #if SK_SUPPORT_GPU
     GrContextOptions grContextOpts;
+    grContextOpts.fGpuPathRenderers = CollectGpuPathRenderersFromFlags();
     gGrFactory.reset(new GrContextFactory(grContextOpts));
 #endif