cc: Make images that can't possibly fit in cache not checker.

cc/tiles/image_controller_unittest.cc

Index: cc/tiles/image_controller_unittest.cc
diff --git a/cc/tiles/image_controller_unittest.cc b/cc/tiles/image_controller_unittest.cc
index 3a89afb2b64961ce543d434e66f98ff2547cbf78..09b7f3ee65c4a41d592829a86a7c732ba596181c 100644
--- a/cc/tiles/image_controller_unittest.cc
+++ b/cc/tiles/image_controller_unittest.cc
@@ -129,6 +129,9 @@ class TestableCache : public ImageDecodeCache {
   void SetShouldAggressivelyFreeResources(
       bool aggressively_free_resources) override {}
   void ClearCache() override {}
+  size_t GetMaximumMemoryLimitBytes() const override {
+    return 256 * 1024 * 1024;
+  }
 
   int number_of_refs() const { return number_of_refs_; }
   void SetTaskToUse(scoped_refptr<TileTask> task) { task_to_use_ = task; }