Forward handling of low-mem message to the content renderer client. Add APIs to handle this case.

chrome/renderer/chrome_render_process_observer.cc

Index: chrome/renderer/chrome_render_process_observer.cc
diff --git a/chrome/renderer/chrome_render_process_observer.cc b/chrome/renderer/chrome_render_process_observer.cc
index bf65d8633de5ea67572e5ce20ac189d23c237fe3..d31884aa8583fbcd005dfea2fb15d3006d8f32b9 100644
--- a/chrome/renderer/chrome_render_process_observer.cc
+++ b/chrome/renderer/chrome_render_process_observer.cc
@@ -19,6 +19,7 @@
 #include "chrome/common/render_messages.h"
 #include "chrome/renderer/content_settings_observer.h"
 #include "chrome/renderer/security_filter_peer.h"
+#include "content/common/notification_source.h"
 #include "content/common/resource_dispatcher.h"
 #include "content/common/resource_dispatcher_delegate.h"
 #include "content/common/view_messages.h"
@@ -391,6 +392,8 @@ ChromeRenderProcessObserver::ChromeRenderProcessObserver() {
   PathService::Get(chrome::DIR_MEDIA_LIBS, &media_path);
   if (!media_path.empty())
     media::InitializeMediaLibrary(media_path);
+
+  registrar_.Add(this, content::NOTIFICATION_PURGE_MEMORY, Source<void>(NULL));
 }
 
 ChromeRenderProcessObserver::~ChromeRenderProcessObserver() {
@@ -413,7 +416,6 @@ bool ChromeRenderProcessObserver::OnControlMessageReceived(
 #endif
     IPC_MESSAGE_HANDLER(ViewMsg_GetV8HeapStats, OnGetV8HeapStats)
     IPC_MESSAGE_HANDLER(ViewMsg_GetCacheResourceStats, OnGetCacheResourceStats)
-    IPC_MESSAGE_HANDLER(ViewMsg_PurgeMemory, OnPurgeMemory)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -481,7 +483,15 @@ void ChromeRenderProcessObserver::OnGetV8HeapStats() {
                                    heap_stats.used_heap_size()));
 }
 
+void ChromeRenderProcessObserver::Observe(int type,
+                                          const NotificationSource& source,
+                                          const NotificationDetails& details) {
+  if (type == content::NOTIFICATION_PURGE_MEMORY)
+    OnPurgeMemory();
+}
+
 void ChromeRenderProcessObserver::OnPurgeMemory() {
+  LOG(INFO) << "CRPO purging memory!";
   // Clear the object cache (as much as possible; some live objects cannot be
   // freed).
   WebCache::clear();