blink MemoryCoordinator::onPurgeMemory should invoke each client's onPurgeMemory.

third_party/WebKit/Source/platform/MemoryCoordinator.cpp

Index: third_party/WebKit/Source/platform/MemoryCoordinator.cpp
diff --git a/third_party/WebKit/Source/platform/MemoryCoordinator.cpp b/third_party/WebKit/Source/platform/MemoryCoordinator.cpp
index b8d6b7ac165e3578e2aa6d786e1d5f6f90303106..c2f7e388e72973d1f8ac46ebf5785e59d8bfd06a 100644
--- a/third_party/WebKit/Source/platform/MemoryCoordinator.cpp
+++ b/third_party/WebKit/Source/platform/MemoryCoordinator.cpp
@@ -68,6 +68,8 @@ void MemoryCoordinator::onMemoryStateChange(MemoryState state) {
 }
 
 void MemoryCoordinator::onPurgeMemory() {
+  for (auto& client : m_clients)
+    client->onPurgeMemory();
   // Don't call clearMemory() because font cache invalidation always causes full
   // layout. This increases tab switching cost significantly (e.g.
   // en.wikipedia.org/wiki/Wikipedia). So we should not invalidate the font