Clear Image Decode Cache on Navigation

cc/tiles/software_image_decode_cache_unittest.cc

Index: cc/tiles/software_image_decode_cache_unittest.cc
diff --git a/cc/tiles/software_image_decode_cache_unittest.cc b/cc/tiles/software_image_decode_cache_unittest.cc
index 8df5b9c8746b4f43d07df17d7a5a7c1ac8e69db9..ec3f0a98d6e46218927ab2885bd0ba9733779633 100644
--- a/cc/tiles/software_image_decode_cache_unittest.cc
+++ b/cc/tiles/software_image_decode_cache_unittest.cc
@@ -1446,5 +1446,28 @@ TEST(SoftwareImageDecodeCacheTest,
   cache.UnrefImage(draw_image_49);
 }
 
+TEST(SoftwareImageDecodeCacheTest, ClearCache) {
+  TestSoftwareImageDecodeCache cache;
+  bool is_decomposable = true;
+  SkFilterQuality quality = kHigh_SkFilterQuality;
+
+  for (int i = 0; i < 10; ++i) {
+    sk_sp<SkImage> image = CreateImage(100, 100);
+    DrawImage draw_image(
+        image, SkIRect::MakeWH(image->width(), image->height()), quality,
+        CreateMatrix(SkSize::Make(1.0f, 1.0f), is_decomposable));
+    scoped_refptr<TileTask> task;
+    bool need_unref = cache.GetTaskForImageAndRef(
+        draw_image, ImageDecodeCache::TracingInfo(), &task);
+    EXPECT_TRUE(need_unref);
+    EXPECT_TRUE(task);
+    TestTileTaskRunner::ProcessTask(task.get());
+    cache.UnrefImage(draw_image);
+  }
+
+  // Tell our cache to clear resources.
+  cache.ClearCache();

[vmpstr, 2017/04/04 00:43:17]

Is there anything we can query to check if the cache is indeed empty? Maybe a
ForTesting function that just returns the number of items or something?

[ericrk, 2017/04/04 17:17:18]

yup - meant to ask you if you were OK with adding this :P - sounds like you are.

+}
+
 }  // namespace
 }  // namespace cc