Bug 1125325 - Store TabParents with their WindowRoot. r=smaug

nsContentUtils::CallOnAllRemoteChildren calls a callback on all tabs
connected to a given window but it has only worked in Firefox e10s tabs.
This patch adds a list of (weak) references to each top-level document's
WindowRoot so that e.g. the nsPresContext can access them instead of
using nsContentUtils.  This provides a solution to the problem of finding remote PBrowsers generally.

dom/base/nsContentUtils.cpp

@@ -7806,3 +7806,16 @@ nsContentUtils::FirePageShowEvent(nsIDocShellTreeItem* aItem,
     doc->OnPageShow(true, aChromeEventHandler);
   }
 }
+
+/* static */
+already_AddRefed<nsPIWindowRoot>
+nsContentUtils::GetWindowRoot(nsIDocument* aDoc)
+{
+  if (aDoc) {
+    nsPIDOMWindow* win = aDoc->GetWindow();
+    if (win) {
+      return win->GetTopWindowRoot();
+    }
+  }
+  return nullptr;
+}

dom/base/nsContentUtils.h

@@ -99,6 +99,7 @@ class nsViewportInfo;
 class nsWrapperCache;
 class nsAttrValue;
 class nsITransferable;
+class nsPIWindowRoot;
 
 struct JSPropertyDescriptor;
 struct JSRuntime;
@@ -2384,6 +2385,8 @@ public:
   static void FirePageHideEvent(nsIDocShellTreeItem* aItem,
                                 mozilla::dom::EventTarget* aChromeEventHandler);
 
+  static already_AddRefed<nsPIWindowRoot> GetWindowRoot(nsIDocument* aDoc);
+
 private:
   static bool InitializeEventTable();
 

dom/base/nsPIWindowRoot.h

@@ -9,14 +9,21 @@
 
 #include "nsISupports.h"
 #include "mozilla/dom/EventTarget.h"
+#include "nsWeakReference.h"
 
 class nsPIDOMWindow;
 class nsIControllers;
 class nsIController;
 
+namespace mozilla {
+namespace dom {
+class TabParent;
+}
+}
+
 #define NS_IWINDOWROOT_IID \
-{ 0x728a2682, 0x55c0, 0x4860, \
- { 0x82, 0x6b, 0x0c, 0x30, 0x0a, 0xac, 0xaa, 0x60 } }
+{ 0x238edca0, 0xb30d, 0x46d3, \
+ { 0xb2, 0x6a, 0x17, 0xb6, 0x21, 0x28, 0x89, 0x7e } }
 
 class nsPIWindowRoot : public mozilla::dom::EventTarget
 {
@@ -38,6 +45,15 @@ public:
 
   virtual void SetParentTarget(mozilla::dom::EventTarget* aTarget) = 0;
   virtual mozilla::dom::EventTarget* GetParentTarget() = 0;
+
+  // Stores a weak reference to the browser.
+  virtual void AddBrowser(mozilla::dom::TabParent* aBrowser) = 0;
+  virtual void RemoveBrowser(mozilla::dom::TabParent* aBrowser) = 0;
+
+  typedef void (*BrowserEnumerator)(mozilla::dom::TabParent* aTab, void* aArg);
+
+  // Enumerate all stored browsers that for which the weak reference is valid.
+  virtual void EnumerateBrowsers(BrowserEnumerator aEnumFunc, void* aArg) = 0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsPIWindowRoot, NS_IWINDOWROOT_IID)

dom/base/nsWindowRoot.cpp

@@ -24,6 +24,7 @@
 #include "nsIController.h"
 #include "xpcpublic.h"
 #include "nsCycleCollectionParticipant.h"
+#include "mozilla/dom/TabParent.h"
 
 #ifdef MOZ_XUL
 #include "nsIDOMXULElement.h"
@@ -385,6 +386,46 @@ nsWindowRoot::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
   return mozilla::dom::WindowRootBinding::Wrap(aCx, this, aGivenProto);
 }
 
+void
+nsWindowRoot::AddBrowser(mozilla::dom::TabParent* aBrowser)
+{
+  nsWeakPtr weakBrowser = do_GetWeakReference(static_cast<nsITabParent*>(aBrowser));
+  mWeakBrowsers.PutEntry(weakBrowser);
+}
+
+void
+nsWindowRoot::RemoveBrowser(mozilla::dom::TabParent* aBrowser)
+{
+  nsWeakPtr weakBrowser = do_GetWeakReference(static_cast<nsITabParent*>(aBrowser));
+  mWeakBrowsers.RemoveEntry(weakBrowser);
+}
+
+static PLDHashOperator
+WeakBrowserEnumFunc(nsRefPtrHashKey<nsIWeakReference>* aKey, void* aArg)
+{
+  nsTArray<nsRefPtr<TabParent>>* tabParents =
+    static_cast<nsTArray<nsRefPtr<TabParent>>*>(aArg);
+  nsCOMPtr<nsITabParent> tabParent(do_QueryReferent((*aKey).GetKey()));
+  TabParent* tab = TabParent::GetFrom(tabParent);
+  if (tab) {
+    tabParents->AppendElement(tab);
+  }
+  return PL_DHASH_NEXT;
+}
+
+void
+nsWindowRoot::EnumerateBrowsers(BrowserEnumerator aEnumFunc, void* aArg)
+{
+  // Collect strong references to all browsers in a separate array in
+  // case aEnumFunc alters mWeakBrowsers.
+  nsTArray<nsRefPtr<TabParent>> tabParents;
+  mWeakBrowsers.EnumerateEntries(WeakBrowserEnumFunc, &tabParents);
+
+  for (uint32_t i = 0; i < tabParents.Length(); ++i) {
+    aEnumFunc(tabParents[i], aArg);
+  }
+}
+
 ///////////////////////////////////////////////////////////////////////////////////
 
 already_AddRefed<EventTarget>

dom/base/nsWindowRoot.h

@@ -69,6 +69,10 @@ public:
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(nsWindowRoot,
                                                          nsIDOMEventTarget)
 
+  virtual void AddBrowser(mozilla::dom::TabParent* aBrowser);
+  virtual void RemoveBrowser(mozilla::dom::TabParent* aBrowser);
+  virtual void EnumerateBrowsers(BrowserEnumerator aEnumFunc, void *aArg);
+
 protected:
   virtual ~nsWindowRoot();
 
@@ -84,6 +88,10 @@ protected:
   nsCOMPtr<nsIDOMNode> mPopupNode; // [OWNER]
 
   nsCOMPtr<mozilla::dom::EventTarget> mParent;
+
+  // The TabParents that are currently registered with this top-level window.
+  typedef nsTHashtable<nsRefPtrHashKey<nsIWeakReference>> WeakBrowserTable;
+  WeakBrowserTable mWeakBrowsers;
 };
 
 extern already_AddRefed<mozilla::dom::EventTarget>

dom/ipc/TabParent.cpp

@@ -334,9 +334,27 @@ TabParent::SetOwnerElement(Element* aElement)
   // If we held previous content then unregister for its events.
   RemoveWindowListeners();
 
+  // If we change top-level documents then we need to change our
+  // registration with them.
+  nsRefPtr<nsPIWindowRoot> curTopLevelWin, newTopLevelWin;
+  if (mFrameElement) {
+    curTopLevelWin = nsContentUtils::GetWindowRoot(mFrameElement->OwnerDoc());
+  }
+  if (aElement) {
+    newTopLevelWin = nsContentUtils::GetWindowRoot(aElement->OwnerDoc());
+  }
+  bool isSameTopLevelWin = curTopLevelWin == newTopLevelWin;
+  if (curTopLevelWin && !isSameTopLevelWin) {
+    curTopLevelWin->RemoveBrowser(this);
+  }
+
   // Update to the new content, and register to listen for events from it.
   mFrameElement = aElement;
 
+  if (newTopLevelWin && !isSameTopLevelWin) {
+    newTopLevelWin->AddBrowser(this);
+  }
+
   AddWindowListeners();
   TryCacheDPIAndScale();
 }
@@ -1001,6 +1019,7 @@ TabParent::UIResolutionChanged()
     // TryCacheDPIAndScale()'s cache is keyed off of
     // mDPI being greater than 0, so this invalidates it.
     mDPI = -1;
+    TryCacheDPIAndScale();
     unused << SendUIResolutionChanged();
   }
 }

layout/base/nsPresContext.cpp

@@ -1822,9 +1822,24 @@ nsPresContext::UIResolutionChangedSubdocumentCallback(nsIDocument* aDocument,
 }
 
 static void
-NotifyUIResolutionChanged(TabParent* aTabParent, void* aArg)
+NotifyTabUIResolutionChanged(TabParent* aTab, void *aArg)
 {
-  aTabParent->UIResolutionChanged();
+  aTab->UIResolutionChanged();
+}
+
+static void
+NotifyChildrenUIResolutionChanged(nsIDOMWindow* aWindow)
+{
+  nsCOMPtr<nsPIDOMWindow> piWin = do_QueryInterface(aWindow);
+  if (!piWin) {
+    return;
+  }
+  nsCOMPtr<nsIDocument> doc = piWin->GetExtantDoc();
+  nsRefPtr<nsPIWindowRoot> topLevelWin = nsContentUtils::GetWindowRoot(doc);
+  if (!topLevelWin) {
+    return;
+  }
+  topLevelWin->EnumerateBrowsers(NotifyTabUIResolutionChanged, nullptr);
 }
 
 void
@@ -1837,10 +1852,8 @@ nsPresContext::UIResolutionChangedInternal()
     AppUnitsPerDevPixelChanged();
   }
 
-  // Recursively notify all remote leaf descendants that the
-  // resolution of the user interface has changed.
-  nsContentUtils::CallOnAllRemoteChildren(mDocument->GetWindow(),
-                                          NotifyUIResolutionChanged, nullptr);
+  // Recursively notify all remote leaf descendants of the change.
+  NotifyChildrenUIResolutionChanged(mDocument->GetWindow());
 
   mDocument->EnumerateSubDocuments(UIResolutionChangedSubdocumentCallback,
                                    nullptr);