notify resource caches when pixelref genID goes stale

src/core/SkResourceCache.cpp

Index: src/core/SkResourceCache.cpp
diff --git a/src/core/SkResourceCache.cpp b/src/core/SkResourceCache.cpp
index ae8412d8b47a323ecd7f5e2f6508629d8d6abcb4..bb159fe1e4baee9f88f1560cc0eaf13852bde9c2 100644
--- a/src/core/SkResourceCache.cpp
+++ b/src/core/SkResourceCache.cpp
@@ -294,6 +294,19 @@ void SkResourceCache::purgeAsNeeded(bool forcePurge) {
     }
 }
 
+void SkResourceCache::purgeVisitor(const void* nameSpace, VisitorProc proc, void* context) {
+    // go backwards, just like purgeAsNeeded, just to make the code similar.
+    // could iterate either direction and still be correct.
+    Rec* rec = fTail;
+    while (rec) {
+        Rec* prev = rec->fPrev;
+        if (rec->getKey().getNamespace() == nameSpace && !proc(*rec, context)) {
+            this->remove(rec);
+        }
+        rec = prev;
+    }
+}
+
 size_t SkResourceCache::setTotalByteLimit(size_t newLimit) {
     size_t prevLimit = fTotalByteLimit;
     fTotalByteLimit = newLimit;
@@ -511,6 +524,11 @@ size_t SkResourceCache::GetSingleAllocationByteLimit() {
     return get_cache()->getSingleAllocationByteLimit();
 }
 
+void SkResourceCache::PurgeVisitor(const void* nameSpace, VisitorProc proc, void* context) {
+    SkAutoMutexAcquire am(gMutex);
+    return get_cache()->purgeVisitor(nameSpace, proc, context);
+}
+
 void SkResourceCache::PurgeAll() {
     SkAutoMutexAcquire am(gMutex);
     return get_cache()->purgeAll();