From ed7f6604e2c572d990f081d93e00675fbaba88bb Mon Sep 17 00:00:00 2001
From: Justin Lebar <justin.lebar@gmail.com>
Date: Mon, 22 Oct 2012 15:40:19 -0400
Subject: [PATCH] Bug 800166 - Fire a low-memory notification when a B2G
 process is backgrounded. r=gwagner,bent

---
 dom/ipc/ProcessPriorityManager.cpp | 7 +++++++
 xpcom/base/nsIMemoryReporter.idl   | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/dom/ipc/ProcessPriorityManager.cpp b/dom/ipc/ProcessPriorityManager.cpp
index ea258633f96..a0b42062ac6 100644
--- a/dom/ipc/ProcessPriorityManager.cpp
+++ b/dom/ipc/ProcessPriorityManager.cpp
@@ -298,6 +298,13 @@ ProcessPriorityManager::OnGracePeriodTimerFired()
 
   mGracePeriodTimer = nullptr;
   hal::SetProcessPriority(getpid(), PROCESS_PRIORITY_BACKGROUND);
+
+  // We're in the background; dump as much memory as we can.
+  nsCOMPtr<nsIMemoryReporterManager> mgr =
+    do_GetService("@mozilla.org/memory-reporter-manager;1");
+  if (mgr) {
+    mgr->MinimizeMemoryUsage(/* callback = */ nullptr);
+  }
 }
 
 } // anonymous namespace
diff --git a/xpcom/base/nsIMemoryReporter.idl b/xpcom/base/nsIMemoryReporter.idl
index f6e6ddc98f5..259a9d81b1a 100644
--- a/xpcom/base/nsIMemoryReporter.idl
+++ b/xpcom/base/nsIMemoryReporter.idl
@@ -295,7 +295,8 @@ interface nsIMemoryReporterManager : nsISupports
 
   /*
    * Run a series of GC/CC's in an attempt to minimize the application's memory
-   * usage.  When we're finished, we invoke the given runnable.
+   * usage.  When we're finished, we invoke the given runnable if it's not
+   * null.
    */
   void minimizeMemoryUsage(in nsIRunnable callback);
 };