ccpr: Use SkMessageBus for thread-safe eviction of cache entries

Bug: skia:
Change-Id: I87725b95761deb689333315ce681a4968d98190a
Reviewed-on: https://skia-review.googlesource.com/c/163511
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/text/GrTextBlobCache.cpp b/src/gpu/text/GrTextBlobCache.cpp
index a60903f..3d8120b 100644
--- a/src/gpu/text/GrTextBlobCache.cpp
+++ b/src/gpu/text/GrTextBlobCache.cpp
@@ -9,6 +9,11 @@
 
 DECLARE_SKMESSAGEBUS_MESSAGE(GrTextBlobCache::PurgeBlobMessage)
 
+static inline bool SkShouldPostMessageToBus(
+        const GrTextBlobCache::PurgeBlobMessage& msg, uint32_t msgBusUniqueID) {
+    return msg.fContextID == msgBusUniqueID;
+}
+
 GrTextBlobCache::~GrTextBlobCache() {
     this->freeAll();
 }