Hook up Context::GetCalling() to V8Proxy.

R=aa
TEST=This will eventually be covered by layout tests once I change the upstream code to use this API.

Review URL: http://codereview.chromium.org/113672

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@16564 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 23 insertions, 3 deletions

diff --git a/webkit/port/bindings/v8/v8_proxy.cpp b/webkit/port/bindings/v8/v8_proxy.cpp
index 03c657d..3f6aa21 100644
--- a/webkit/port/bindings/v8/v8_proxy.cpp
+++ b/webkit/port/bindings/v8/v8_proxy.cpp
@@ -1653,6 +1653,15 @@ Frame* V8Proxy::retrieveFrameForCurrentContext()
 }
 
 
+Frame* V8Proxy::retrieveFrameForCallingContext()
+{
+    v8::Handle<v8::Context> context = v8::Context::GetCalling();
+    if (context.IsEmpty())
+        return 0;
+    return retrieveFrame(context);
+}
+
+
 Frame* V8Proxy::retrieveFrame()
 {
     DOMWindow* window = retrieveWindow();
diff --git a/webkit/port/bindings/v8/v8_proxy.h b/webkit/port/bindings/v8/v8_proxy.h
index 4cb6892..c2bb66f 100644
--- a/webkit/port/bindings/v8/v8_proxy.h
+++ b/webkit/port/bindings/v8/v8_proxy.h
@@ -285,9 +285,9 @@ class V8Proxy {
   static Frame* retrieveFrame(v8::Handle<v8::Context> context);
 
 
-  // The two functions below retrieve WebFrame instances relating the currently
-  // executing JavaScript. Since JavaScript can make function calls across
-  // frames, though, we need to be more precise.
+  // The three functions below retrieve WebFrame instances relating the
+  // currently executing JavaScript. Since JavaScript can make function calls
+  // across frames, though, we need to be more precise.
   //
   // For example, imagine that a JS function in frame A calls a function in
   // frame B, which calls native code, which wants to know what the 'active'
@@ -296,15 +296,26 @@ class V8Proxy {
   // The 'entered context' is the context where execution first entered the
   // script engine; the context that is at the bottom of the JS function stack.
   // RetrieveFrameForEnteredContext() would return Frame A in our example.
+  // This frame is often referred to as the "dynamic global object."
   //
   // The 'current context' is the context the JS engine is currently inside of;
   // the context that is at the top of the JS function stack.
   // RetrieveFrameForCurrentContext() would return Frame B in our example.
+  // This frame is often referred to as the "lexical global object."
+  //
+  // Finally, the 'calling context' is the context one below the current
+  // context on the JS function stack.  For example, if function f calls
+  // function g, then the calling context will be the context associated with
+  // f.  This context is commonly used by DOM security checks because they want
+  // to know who called them.
+  //
+  // If you are unsure which of these functions to use, ask abarth.
   //
   // NOTE: These cannot be declared as inline function, because VS complains at
   // linking time.
   static Frame* retrieveFrameForEnteredContext();
   static Frame* retrieveFrameForCurrentContext();
+  static Frame* retrieveFrameForCallingContext();
 
   // Returns V8 Context of a frame. If none exists, creates
   // a new context.  It is potentially slow and consumes memory.