[Interpreter] Adds support to fetch return value on break at return.

src/debug/debug.h

Index: src/debug/debug.h
diff --git a/src/debug/debug.h b/src/debug/debug.h
index 600bc1a605bd6349f20faa983b473050ab5a3d9e..b8a223f515f132c6f3a2a16e965beccc6beba53e 100644
--- a/src/debug/debug.h
+++ b/src/debug/debug.h
@@ -524,6 +524,8 @@ class Debug {
   StackFrame::Id break_frame_id() { return thread_local_.break_frame_id_; }
   int break_id() { return thread_local_.break_id_; }
 
+  Handle<Object> get_return_value() { return thread_local_.return_value_; }
+
   // Support for embedding into generated code.
   Address is_active_address() {
     return reinterpret_cast<Address>(&is_active_);
@@ -678,6 +680,10 @@ class Debug {
     // Stores the way how LiveEdit has patched the stack. It is used when
     // debugger returns control back to user script.
     LiveEdit::FrameDropMode frame_drop_mode_;
+
+    // Value of accumulator in interpreter frames. In non-interpreter frames
+    // this value will be a hole.

[rmcilroy, 2016/03/22 11:32:34]

/s/a hole/the hole/

[mythria, 2016/03/22 12:08:09]

Done.

+    Handle<Object> return_value_;
   };
 
   // Storage location for registers when handling debug break calls
@@ -719,6 +725,7 @@ class DebugScope BASE_EMBEDDED {
   DebugScope* prev_;               // Previous scope if entered recursively.
   StackFrame::Id break_frame_id_;  // Previous break frame id.
   int break_id_;                   // Previous break id.
+  Handle<Object> return_value_;    // Previous result.
   bool failed_;                    // Did the debug context fail to load?
   SaveContext save_;               // Saves previous context.
   PostponeInterruptsScope no_termination_exceptons_;