[Isolates] Convert more static data either to read-only or to per-isolate.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 754a5a0cd23fefce2d6f1d2c40e4c28102d8347d..2cd8a2d729163bf0f5cd124ab33e88e25e8eacee 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -1764,7 +1764,7 @@ void Debug::SetAfterBreakTarget(JavaScriptFrame* frame) {
   Handle<Code> original_code(debug_info->original_code());
 #ifdef DEBUG
   // Get the code which is actually executing.
-  Handle<Code> frame_code(frame->code());
+  Handle<Code> frame_code(frame->LookupCode(Isolate::Current()));
   ASSERT(frame_code.is_identical_to(code));
 #endif
 
@@ -1846,7 +1846,7 @@ bool Debug::IsBreakAtReturn(JavaScriptFrame* frame) {
   Handle<Code> code(debug_info->code());
 #ifdef DEBUG
   // Get the code which is actually executing.
-  Handle<Code> frame_code(frame->code());
+  Handle<Code> frame_code(frame->LookupCode(Isolate::Current()));
   ASSERT(frame_code.is_identical_to(code));
 #endif