Bug 1337730 - part1: releaseCachedProcesses API for testing. r=mrbkap

dom/base/nsFrameMessageManager.cpp

@@ -35,7 +35,7 @@
 #include "mozilla/Telemetry.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/MessagePort.h"
-#include "mozilla/dom/nsIContentParent.h"
+#include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/PermissionMessageUtils.h"
 #include "mozilla/dom/ProcessGlobal.h"
 #include "mozilla/dom/SameProcessMessageQueue.h"
@@ -778,6 +778,12 @@ nsFrameMessageManager::GetChildAt(uint32_t aIndex,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsFrameMessageManager::ReleaseCachedProcesses()
+{
+  ContentParent::ReleaseCachedProcesses();
+  return NS_OK;
+}
 
 // nsIContentFrameMessageManager
 

dom/base/nsIMessageManager.idl

@@ -327,6 +327,12 @@ interface nsIMessageBroadcaster : nsIMessageListenerManager
    * Return a single subordinate message manager.
    */
   nsIMessageListenerManager getChildAt(in unsigned long aIndex);
+
+  /**
+   * Some processes are kept alive after their last tab/window are closed for testing
+   * (see dom.ipc.keepProcessesAlive). This function releases those.
+   */
+   void releaseCachedProcesses();
 };
 
 [scriptable, builtinclass, uuid(0e602c9e-1977-422a-a8e4-fe0d4a4f78d0)]

dom/ipc/ContentParent.cpp

@@ -650,6 +650,32 @@ ContentParent::IsMaxProcessCountReached(const nsAString& aContentProcessType)
   return GetPoolSize(aContentProcessType) >= GetMaxProcessCount(aContentProcessType);
 }
 
+/*static*/ void
+ContentParent::ReleaseCachedProcesses()
+{
+  // We might want to extend this for other process types as well in the future...
+  nsTArray<ContentParent*>& contentParents = GetOrCreatePool(NS_LITERAL_STRING(DEFAULT_REMOTE_TYPE));
+  ContentProcessManager* cpm = ContentProcessManager::GetSingleton();
+  nsTArray<ContentParent*> toRelease;
+
+  // Shuting down these processes will change the array so let's use another array for the removal.
+  for (auto* cp : contentParents) {
+    nsTArray<TabId> tabIds = cpm->GetTabParentsByProcessId(cp->mChildID);
+    if (!tabIds.Length()) {
+      toRelease.AppendElement(cp);
+    }
+  }
+
+  for (auto* cp : toRelease) {
+    // Start a soft shutdown.
+    cp->ShutDownProcess(SEND_SHUTDOWN_MESSAGE);
+    // Make sure we don't select this process for new tabs.
+    cp->MarkAsDead();
+    // Make sure that this process is no longer accessible from JS by its message manager.
+    cp->ShutDownMessageManager();
+  }
+}
+
 /*static*/ already_AddRefed<ContentParent>
 ContentParent::RandomSelect(const nsTArray<ContentParent*>& aContentParents,
                             ContentParent* aOpener, int32_t aMaxContentParents)

dom/ipc/ContentParent.h

@@ -153,6 +153,8 @@ public:
 
   static bool IsMaxProcessCountReached(const nsAString& aContentProcessType);
 
+  static void ReleaseCachedProcesses();
+
   /**
    * Picks a random content parent from |aContentParents| with a given |aOpener|
    * respecting the index limit set by |aMaxContentParents|.