Bug 1516240 - Part 2: Allow serializing BrowsingContext over IPC, r=farre

This patch takes the approach of taking a reference, so that we can land
it into the tree more quickly & fix issues we have.

This isn't a final solution by any means, we should also do something
along the lines of the StableState approach, but it should be sufficient
for now.

Depends on D19177

Differential Revision: https://phabricator.services.mozilla.com/D19178

--HG--
extra : moz-landing-system : lando

docshell/base/BrowsingContext.cpp

@@ -515,4 +515,46 @@ already_AddRefed<BrowsingContext> BrowsingContext::FindChildWithName(
 }
 
 }  // namespace dom
+
+namespace ipc {
+
+void IPDLParamTraits<dom::BrowsingContext>::Write(
+    IPC::Message* aMsg, IProtocol* aActor, dom::BrowsingContext* aParam) {
+  uint64_t id = aParam ? aParam->Id() : 0;
+  WriteIPDLParam(aMsg, aActor, id);
+
+  // If his is an in-process send. We want to make sure that our BrowsingContext
+  // object lives long enough to make it to the other side, so we take an extra
+  // reference. This reference is freed in ::Read().
+  if (!aActor->GetIPCChannel()->IsCrossProcess()) {
+    NS_IF_ADDREF(aParam);
+  }
+}
+
+bool IPDLParamTraits<dom::BrowsingContext>::Read(
+    const IPC::Message* aMsg, PickleIterator* aIter, IProtocol* aActor,
+    RefPtr<dom::BrowsingContext>* aResult) {
+  uint64_t id = 0;
+  if (!ReadIPDLParam(aMsg, aIter, aActor, &id)) {
+    return false;
+  }
+
+  if (id == 0) {
+    aResult = nullptr;
+    return true;
+  }
+
+  *aResult = dom::BrowsingContext::Get(id);
+  MOZ_ASSERT(aResult, "Deserialized absent BrowsingContext!");
+
+  // If this is an in-process actor, free the reference taken in ::Write().
+  if (!aActor->GetIPCChannel()->IsCrossProcess()) {
+    dom::BrowsingContext* bc = *aResult;
+    NS_IF_RELEASE(bc);
+  }
+
+  return aResult != nullptr;
+}
+
+}  // namespace ipc
 }  // namespace mozilla

docshell/base/BrowsingContext.h

@@ -20,6 +20,11 @@
 
 class nsGlobalWindowOuter;
 class nsOuterWindowProxy;
+class PickleIterator;
+
+namespace IPC {
+class Message;
+}  // namespace IPC
 
 namespace mozilla {
 
@@ -27,6 +32,13 @@ class ErrorResult;
 class LogModule;
 class OOMReporter;
 
+namespace ipc {
+class IProtocol;
+
+template <typename T>
+struct IPDLParamTraits;
+}  // namespace ipc
+
 namespace dom {
 
 class BrowsingContextGroup;
@@ -254,6 +266,17 @@ extern bool GetRemoteOuterWindowProxy(JSContext* aCx, BrowsingContext* aContext,
                                       JS::MutableHandle<JSObject*> aRetVal);
 
 }  // namespace dom
+
+// Allow sending BrowsingContext objects over IPC.
+namespace ipc {
+template <>
+struct IPDLParamTraits<dom::BrowsingContext> {
+  static void Write(IPC::Message* aMsg, IProtocol* aActor,
+                    dom::BrowsingContext* aParam);
+  static bool Read(const IPC::Message* aMsg, PickleIterator* aIter,
+                   IProtocol* aActor, RefPtr<dom::BrowsingContext>* aResult);
+};
+}  // namespace ipc
 }  // namespace mozilla
 
 #endif  // !defined(mozilla_dom_BrowsingContext_h)

dom/ipc/WindowGlobalParent.h

@@ -22,6 +22,7 @@ namespace dom {
 class CanonicalBrowsingContext;
 class WindowGlobalChild;
 class JSWindowActorParent;
+class TabParent;
 
 /**
  * A handle in the parent process to a specific nsGlobalWindowInner object.