Reland "Make GPU cache invalidation SkMessageBus messages go to one GrContext."

This is a reland of f4c5bb9aba485aa47c27b15905d81992b7cf4707

Original change's description:
> Make GPU cache invalidation SkMessageBus messages go to one GrContext.
> 
> Makes it so the template param to SkMessageBus must implement:
> bool shouldSend(uint32_t inboxID) const
> 
> Updates all GPU backend message types to only go to the GrContext that
> is adding a cache entry.
> 
> Bug: skia:
> Change-Id: I3e8a4eb90654b7b8ac57cac9fb508c0ef1d51058
> Reviewed-on: https://skia-review.googlesource.com/140220
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Reviewed-by: Jim Van Verth <jvanverth@google.com>

Bug: skia:
Change-Id: I8402bfe3ed0170c99936d47050458817030b473b
Reviewed-on: https://skia-review.googlesource.com/140801
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/ops/GrTessellatingPathRenderer.cpp b/src/gpu/ops/GrTessellatingPathRenderer.cpp
index 1c0a7f5..475197e 100644
--- a/src/gpu/ops/GrTessellatingPathRenderer.cpp
+++ b/src/gpu/ops/GrTessellatingPathRenderer.cpp
@@ -42,7 +42,9 @@
 // When the SkPathRef genID changes, invalidate a corresponding GrResource described by key.
 class PathInvalidator : public SkPathRef::GenIDChangeListener {
 public:
-    explicit PathInvalidator(const GrUniqueKey& key) : fMsg(key) {}
+    PathInvalidator(const GrUniqueKey& key, uint32_t contextUniqueID)
+            : fMsg(key, contextUniqueID) {}
+
 private:
     GrUniqueKeyInvalidatedMessage fMsg;
 
@@ -284,7 +286,7 @@
         info.fCount = count;
         key.setCustomData(SkData::MakeWithCopy(&info, sizeof(info)));
         rp->assignUniqueKeyToResource(key, allocator.vertexBuffer());
-        fShape.addGenIDChangeListener(sk_make_sp<PathInvalidator>(key));
+        fShape.addGenIDChangeListener(sk_make_sp<PathInvalidator>(key, target->contextUniqueID()));
     }
 
     void drawAA(Target* target, const GrGeometryProcessor* gp, size_t vertexStride) {