Move purging from OnMemoryState to OnPurgeMemory() in cc/

cc/tiles/software_image_decode_cache.cc

Index: cc/tiles/software_image_decode_cache.cc
diff --git a/cc/tiles/software_image_decode_cache.cc b/cc/tiles/software_image_decode_cache.cc
index aa2066592517f744eaaaa1020d2ce9bf5d26c61d..1248a2545c5199d161469e3682ac6eaf256a3e44 100644
--- a/cc/tiles/software_image_decode_cache.cc
+++ b/cc/tiles/software_image_decode_cache.cc
@@ -783,12 +783,10 @@ void SoftwareImageDecodeCache::UnrefAtRasterImage(const ImageKey& key) {
   }
 }
 
-void SoftwareImageDecodeCache::ReduceCacheUsage() {
+void SoftwareImageDecodeCache::ReduceCacheUsageUntilWithinLimit(size_t limit) {
   TRACE_EVENT0("cc", "SoftwareImageDecodeCache::ReduceCacheUsage");
-  base::AutoLock lock(lock_);
-  size_t num_to_remove = (decoded_images_.size() > max_items_in_cache_)
-                             ? (decoded_images_.size() - max_items_in_cache_)
-                             : 0;
+  size_t num_to_remove =
+      (decoded_images_.size() > limit) ? (decoded_images_.size() - limit) : 0;
   for (auto it = decoded_images_.rbegin();
        num_to_remove != 0 && it != decoded_images_.rend();) {
     if (it->second->is_locked()) {
@@ -801,6 +799,11 @@ void SoftwareImageDecodeCache::ReduceCacheUsage() {
   }
 }
 
+void SoftwareImageDecodeCache::ReduceCacheUsage() {
+  base::AutoLock lock(lock_);
+  ReduceCacheUsageUntilWithinLimit(max_items_in_cache_);
+}
+
 void SoftwareImageDecodeCache::RemovePendingTask(const ImageKey& key,
                                                  DecodeTaskType task_type) {
   base::AutoLock lock(lock_);
@@ -1160,7 +1163,17 @@ void SoftwareImageDecodeCache::OnMemoryStateChange(base::MemoryState state) {
         return;
     }
   }
-  ReduceCacheUsage();
+  // TODO(bashi): We are going to separate purging from state changes and we
+  // shouldn't purge memory here (crbug.com/684287). Tentatively call
+  // OnPurgeMemory() so that we don't break existing experiments.
+  // (i.e. purge+suspend experiment)
+  if (state == base::MemoryState::SUSPENDED)
+    OnPurgeMemory();

[ericrk, 2017/01/30 15:58:56]

This also removes the ability to handle THROTTLED state, is this intentional? I
think we just want "ReduceCacheUsage" here.

[bashi, 2017/01/31 19:30:56]

Yes, it's intentional. I'm going to move ReduceCacheUsage() call from
OnStateChange() to OnPurgeMemory(). We need to keep purging memory here because
currently purge+suspend experiment depends on this behavior. When I complete
updating all clients (this CL is the first one), and purge+suspend experiment
I'll remove this lines.

+}
+
+void SoftwareImageDecodeCache::OnPurgeMemory() {
+  base::AutoLock lock(lock_);
+  ReduceCacheUsageUntilWithinLimit(0);
 }
 
 }  // namespace cc