Setup CCPR testing with GrMockContext

Beefs up the mock context to be able to support CCPR, sets up a
framework for testing CCPR with the mock context, and adds a new test.

Bug: skia:
Change-Id: If95f92726f7b1a7f52ad04ca8126551f58ea8032
Reviewed-on: https://skia-review.googlesource.com/67980
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/GrDrawingManager.h b/src/gpu/GrDrawingManager.h
index 38d2349..f78229f 100644
--- a/src/gpu/GrDrawingManager.h
+++ b/src/gpu/GrDrawingManager.h
@@ -18,6 +18,7 @@
 #include "text/GrAtlasTextContext.h"
 
 class GrContext;
+class GrCoverageCountingPathRenderer;
 class GrOnFlushCallbackObject;
 class GrRenderTargetContext;
 class GrRenderTargetProxy;
@@ -62,6 +63,10 @@
                                     GrPathRendererChain::DrawType drawType,
                                     GrPathRenderer::StencilSupport* stencilSupport = nullptr);
 
+    // Returns a direct pointer to the coverage counting path renderer, or null if it is not
+    // supported and turned on.
+    GrCoverageCountingPathRenderer* getCoverageCountingPathRenderer();
+
     void flushIfNecessary() {
         if (fContext->getResourceCache()->requestsFlush()) {
             this->internalFlush(nullptr, GrResourceCache::kCacheRequested, 0, nullptr);