From 18136e92bdffbdda5b3df856c454437fd778e1b4 Mon Sep 17 00:00:00 2001
From: Jon Hylands <jhylands@mozilla.com>
Date: Tue, 16 Apr 2013 15:34:11 +0200
Subject: [PATCH] Bug 853632 - Cache own and containing apps in TabContext.
 r=jlebar

---
 dom/ipc/TabContext.cpp | 26 ++++++++++++++++++++++++++
 dom/ipc/TabContext.h   | 20 +++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/dom/ipc/TabContext.cpp b/dom/ipc/TabContext.cpp
index f0975f5bf87..4f5e44f5aa3 100644
--- a/dom/ipc/TabContext.cpp
+++ b/dom/ipc/TabContext.cpp
@@ -294,6 +294,32 @@ TabContext::GetAppForId(uint32_t aAppId) const
     return nullptr;
   }
 
+  // This application caching is needed to avoid numerous unecessary application clones.
+  // See Bug 853632 for details.
+
+  if (aAppId == mOwnAppId) {
+    if (!mOwnApp) {
+      mOwnApp = GetAppForIdNoCache(aAppId);
+    }
+    nsCOMPtr<mozIApplication> ownApp = mOwnApp;
+    return ownApp.forget();
+  }
+
+  if (aAppId == mContainingAppId) {
+    if (!mContainingApp) {
+      mContainingApp = GetAppForIdNoCache(mContainingAppId);
+    }
+    nsCOMPtr<mozIApplication> containingApp = mContainingApp;
+    return containingApp.forget();
+  }
+  // We need the fallthrough here because mOwnAppId/mContainingAppId aren't always
+  // set before calling GetAppForId().
+  return GetAppForIdNoCache(aAppId);
+}
+
+already_AddRefed<mozIApplication>
+TabContext::GetAppForIdNoCache(uint32_t aAppId) const
+{
   nsCOMPtr<nsIAppsService> appsService = do_GetService(APPS_SERVICE_CONTRACTID);
   NS_ENSURE_TRUE(appsService, nullptr);
 
diff --git a/dom/ipc/TabContext.h b/dom/ipc/TabContext.h
index b9ecd44865c..cf45018f51e 100644
--- a/dom/ipc/TabContext.h
+++ b/dom/ipc/TabContext.h
@@ -159,10 +159,15 @@ protected:
 
 private:
   /**
-   * Translate an appId into a mozIApplication.
+   * Translate an appId into a mozIApplication, using lazy caching.
    */
   already_AddRefed<mozIApplication> GetAppForId(uint32_t aAppId) const;
 
+  /**
+   * Translate an appId into a mozIApplication.
+   */
+  already_AddRefed<mozIApplication> GetAppForIdNoCache(uint32_t aAppId) const;
+
   /**
    * Has this TabContext been initialized?  If so, mutator methods will fail.
    */
@@ -174,6 +179,12 @@ private:
    */
   uint32_t mOwnAppId;
 
+  /**
+   * Cache of this TabContext's own app.  If mOwnAppId is NO_APP_ID, this is
+   * guaranteed to be nullptr.  Otherwise, it may or may not be null.
+   */
+  mutable nsCOMPtr<mozIApplication> mOwnApp;
+
   /**
    * The id of the app which contains this TabContext's frame.  If mIsBrowser,
    * this corresponds to the ID of the app which contains the browser frame;
@@ -182,6 +193,13 @@ private:
    */
   uint32_t mContainingAppId;
 
+  /**
+   * Cache of the app that contains this TabContext's frame.  If mContainingAppId
+   * is NO_APP_ID, this is guaranteed to be nullptr.  Otherwise, it may or may not
+   * be null.
+   */
+  mutable nsCOMPtr<mozIApplication> mContainingApp;
+
   /**
    * The requested scrolling behavior for this frame.
    */