Bug 1444604: Part 6: Add LiveSavedFrameCache::findWithoutInvalidation. r=jorendorff

--HG--
extra : rebase_source : bbe26f26f0ae8e0f30e6505e1614c3ae4a320300
extra : histedit_source : fa29282837885902c7a5413cce34ef71e8b444d3

js/src/vm/SavedStacks.cpp

@@ -156,6 +156,24 @@ LiveSavedFrameCache::find(JSContext* cx, FramePtr& framePtr, const jsbytecode* p
     frame.set(frames->back().savedFrame);
 }
 
+void
+LiveSavedFrameCache::findWithoutInvalidation(const FramePtr& framePtr,
+                                             MutableHandleSavedFrame frame) const
+{
+    MOZ_ASSERT(initialized());
+    MOZ_ASSERT(framePtr.hasCachedSavedFrame());
+
+    Key key(framePtr);
+    for (auto& entry : (*frames)) {
+        if (entry.key == key) {
+            frame.set(entry.savedFrame);
+            return;
+        }
+    }
+
+    frame.set(nullptr);
+}
+
 struct SavedFrame::Lookup {
     Lookup(JSAtom* source, uint32_t line, uint32_t column,
            JSAtom* functionDisplayName, JSAtom* asyncCause, SavedFrame* parent,

js/src/vm/Stack.h

@@ -1357,6 +1357,11 @@ class LiveSavedFrameCache
     void find(JSContext* cx, FramePtr& framePtr, const jsbytecode* pc,
               MutableHandleSavedFrame frame) const;
 
+    // Search the cache for a frame matching |framePtr|, without removing any
+    // entries. Return the matching saved frame, or nullptr if none is found.
+    // This is used for resolving |evalInFramePrev| links.
+    void findWithoutInvalidation(const FramePtr& framePtr, MutableHandleSavedFrame frame) const;
+
     // Push a cache entry mapping |framePtr| and |pc| to |savedFrame| on the top
     // of the cache's stack. You must insert entries for frames from oldest to
     // youngest. They must all be younger than the frame that the |find| method