Find the correct function for script break points

The algorithm for finding the inner-most function containing a script break point was not correct when the script only contained one function. In that case the script function and not the actual function in the script could be returned depending on the order of the objects in the heap.

TEST=cctest/test-debug/ScriptBreakPointReload
BUG=none

Review URL: http://codereview.chromium.org/193059

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2862 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.h

@@ -3105,9 +3105,7 @@ class SharedFunctionInfo: public HeapObject {
   inline bool is_expression();
   inline void set_is_expression(bool value);
 
-  // Is this function a top-level function. Used for accessing the
-  // caller of functions. Top-level functions (scripts, evals) are
-  // returned as null; see JSFunction::GetCallerAccessor(...).
+  // Is this function a top-level function (scripts, evals).
   inline bool is_toplevel();
   inline void set_is_toplevel(bool value);
 

src/runtime.cc

@@ -6821,8 +6821,20 @@ Object* Runtime::FindSharedFunctionInfoInScript(Handle<Script> script,
               target_start_position = start_position;
               target = shared;
             } else {
-              if (target_start_position < start_position &&
-                  shared->end_position() < target->end_position()) {
+              if (target_start_position == start_position &&
+                  shared->end_position() == target->end_position()) {
+                  // If a top-level function contain only one function
+                  // declartion the source for the top-level and the function is
+                  // the same. In that case prefer the non top-level function.
+                if (!shared->is_toplevel()) {
+                  target_start_position = start_position;
+                  target = shared;
+                }
+              } else if (target_start_position <= start_position &&
+                         shared->end_position() <= target->end_position()) {
+                // This containment check includes equality as a function inside
+                // a top-level function can share either start or end position
+                // with the top-level function.
                 target_start_position = start_position;
                 target = shared;
               }