Dump out path-mask generation and caching stats

These stats would've helped block https://skia-review.googlesource.com/c/skia/+/286902 (Add path bounds to SW path mask key) from landing.

Change-Id: I684f39de53fb2678c7a679e4e4aafdbb39a154ca
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/287499
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index fce2526..52b6e4b 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -683,6 +683,9 @@
     writer.appendName("gpu");
     this->fGpu->dumpJSON(&writer);
 
+    writer.appendName("context");
+    this->dumpJSON(&writer);
+
     // Flush JSON to the memory stream
     writer.endObject();
     writer.flush();