From 333122f56408d9b3f82708fd1b641740dd0b3d8d Mon Sep 17 00:00:00 2001
From: Mats Palmgren <matspal@gmail.com>
Date: Mon, 1 Apr 2013 18:45:19 +0200
Subject: [PATCH] Bug 856243 - Add missing do_QueryFrame support.  r=dholbert

---
 layout/generic/nsFrameSetFrame.cpp |  1 +
 layout/generic/nsHTMLCanvasFrame.h |  1 +
 layout/generic/nsQueryFrame.h      | 12 +++++++-----
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/layout/generic/nsFrameSetFrame.cpp b/layout/generic/nsFrameSetFrame.cpp
index 3c6059fff225..420ca7f6c3b2 100644
--- a/layout/generic/nsFrameSetFrame.cpp
+++ b/layout/generic/nsFrameSetFrame.cpp
@@ -142,6 +142,7 @@ protected:
 class nsHTMLFramesetBlankFrame : public nsLeafFrame
 {
 public:
+  NS_DECL_QUERYFRAME_TARGET(nsHTMLFramesetBlankFrame)
   NS_DECL_FRAMEARENA_HELPERS
 
 #ifdef DEBUG
diff --git a/layout/generic/nsHTMLCanvasFrame.h b/layout/generic/nsHTMLCanvasFrame.h
index e67072808816..ed564aa4ddc2 100644
--- a/layout/generic/nsHTMLCanvasFrame.h
+++ b/layout/generic/nsHTMLCanvasFrame.h
@@ -34,6 +34,7 @@ public:
   typedef mozilla::layers::LayerManager LayerManager;
   typedef mozilla::FrameLayerBuilder::ContainerParameters ContainerParameters;
 
+  NS_DECL_QUERYFRAME_TARGET(nsHTMLCanvasFrame)
   NS_DECL_FRAMEARENA_HELPERS
 
   nsHTMLCanvasFrame(nsStyleContext* aContext) : nsContainerFrame(aContext) {}
diff --git a/layout/generic/nsQueryFrame.h b/layout/generic/nsQueryFrame.h
index 589df3360811..c20956791e92 100644
--- a/layout/generic/nsQueryFrame.h
+++ b/layout/generic/nsQueryFrame.h
@@ -8,7 +8,8 @@
 #include "nscore.h"
 
 #define NS_DECL_QUERYFRAME_TARGET(classname)                    \
-  static const nsQueryFrame::FrameIID kFrameIID = nsQueryFrame::classname##_id;
+  static const nsQueryFrame::FrameIID kFrameIID = nsQueryFrame::classname##_id; \
+  typedef classname* Has_NS_DECL_QUERYFRAME_TARGET;
 
 #define NS_DECL_QUERYFRAME                                      \
   virtual void* QueryFrame(FrameIID id);
@@ -33,7 +34,7 @@
 #define NS_QUERYFRAME_TAIL_INHERITANCE_ROOT                     \
   default: break;                                               \
   }                                                             \
-  return nullptr;                                                \
+  return nullptr;                                               \
 }
 
 class nsQueryFrame
@@ -63,9 +64,10 @@ public:
 
   template<class Dest>
   operator Dest*() {
-    if (!mRawPtr)
-      return nullptr;
-
+    if (!mRawPtr) {
+      // Ensure that Dest declared itself as a queryframe target.
+      return static_cast<typename Dest::Has_NS_DECL_QUERYFRAME_TARGET>(nullptr);
+    }
     return reinterpret_cast<Dest*>(mRawPtr->QueryFrame(Dest::kFrameIID));
   }