Notify resource caches when pixelref genID goes stale

tests/ImageCacheTest.cpp

Index: tests/ImageCacheTest.cpp
diff --git a/tests/ImageCacheTest.cpp b/tests/ImageCacheTest.cpp
index a4cfa739890ff08167cc2e959d3a965471ac231c..45dee92a2f02ba4b37436a80732564fb55be7938 100644
--- a/tests/ImageCacheTest.cpp
+++ b/tests/ImageCacheTest.cpp
@@ -14,8 +14,8 @@ static void* gGlobalAddress;
 struct TestingKey : public SkResourceCache::Key {
     intptr_t    fValue;
 
-    TestingKey(intptr_t value) : fValue(value) {
-        this->init(&gGlobalAddress, sizeof(fValue));
+    TestingKey(intptr_t value, uint64_t sharedID = 0) : fValue(value) {
+        this->init(&gGlobalAddress, sharedID, sizeof(fValue));
     }
 };
 struct TestingRec : public SkResourceCache::Rec {
@@ -71,6 +71,38 @@ static void test_cache(skiatest::Reporter* reporter, SkResourceCache& cache, boo
     cache.setTotalByteLimit(0);
 }
 
+static void test_cache_purge_shared_id(skiatest::Reporter* reporter, SkResourceCache& cache) {
+    for (int i = 0; i < COUNT; ++i) {
+        TestingKey key(i, i & 1);   // every other key will have a 1 for its sharedID        
+        cache.add(SkNEW_ARGS(TestingRec, (key, i)));
+    }
+
+    // Ensure that everyone is present
+    for (int i = 0; i < COUNT; ++i) {
+        TestingKey key(i, i & 1);   // every other key will have a 1 for its sharedID
+        intptr_t value = -1;
+
+        REPORTER_ASSERT(reporter, cache.find(key, TestingRec::Visitor, &value));
+        REPORTER_ASSERT(reporter, value == i);
+    }
+
+    // Now purge the ones that had a non-zero sharedID (the odd-indexed ones)
+    cache.purgeSharedID(1);
+
+    // Ensure that only the even ones are still present
+    for (int i = 0; i < COUNT; ++i) {
+        TestingKey key(i, i & 1);   // every other key will have a 1 for its sharedID
+        intptr_t value = -1;
+
+        if (i & 1) {
+            REPORTER_ASSERT(reporter, !cache.find(key, TestingRec::Visitor, &value));
+        } else {
+            REPORTER_ASSERT(reporter, cache.find(key, TestingRec::Visitor, &value));
+            REPORTER_ASSERT(reporter, value == i);
+        }
+    }
+}
+
 #include "SkDiscardableMemoryPool.h"
 
 static SkDiscardableMemoryPool* gPool;
@@ -97,6 +129,10 @@ DEF_TEST(ImageCache, reporter) {
         SkResourceCache cache(SkDiscardableMemory::Create);
         test_cache(reporter, cache, false);
     }
+    {
+        SkResourceCache cache(defLimit);
+        test_cache_purge_shared_id(reporter, cache);
+    }
 }
 
 DEF_TEST(ImageCache_doubleAdd, r) {