Restore behavior of PrepareForBreakpoints which was broken by r21145.

Rename Debug::MaybeRecompileFunctionForDebugging to
EnsureFunctionHasDebugBreakSlots and ensure that it does
nothing if the function is unoptimized code with debug
break slots, otherwise, if the shared code has no
debug break slots, it recompile that shared code and
sets the function code to that shared code.

Also removes two incorrect ASSERTs.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/271873003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21201 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/debug.cc

@@ -2037,18 +2037,25 @@ class ForceDebuggerActive {
 };
 
 
-void Debug::MaybeRecompileFunctionForDebugging(Handle<JSFunction> function) {
-  ASSERT_EQ(Code::FUNCTION, function->code()->kind());
-  ASSERT_EQ(function->code(), function->shared()->code());
+void Debug::EnsureFunctionHasDebugBreakSlots(Handle<JSFunction> function) {
+  if (function->code()->kind() == Code::FUNCTION &&
+      function->code()->has_debug_break_slots()) {
+    // Nothing to do. Function code already had debug break slots.
+    return;
+  }
 
-  if (function->code()->has_debug_break_slots()) return;
+  // Make sure that the shared full code is compiled with debug
+  // break slots.
+  if (!function->shared()->code()->has_debug_break_slots()) {
+    ForceDebuggerActive force_debugger_active(isolate_);
+    MaybeHandle<Code> code = Compiler::GetCodeForDebugging(function);
+    // Recompilation can fail.  In that case leave the code as it was.
+    if (!code.is_null())
+      function->ReplaceCode(*code.ToHandleChecked());
+  }
 
-  ForceDebuggerActive force_debugger_active(isolate_);
-  MaybeHandle<Code> code = Compiler::GetCodeForDebugging(function);
-  // Recompilation can fail.  In that case leave the code as it was.
-  if (!code.is_null())
-    function->ReplaceCode(*code.ToHandleChecked());
-  ASSERT_EQ(function->code(), function->shared()->code());
+  // Keep function code in sync with shared function info.
+  function->ReplaceCode(function->shared()->code());
 }
 
 
@@ -2057,7 +2064,7 @@ void Debug::RecompileAndRelocateSuspendedGenerators(
   for (int i = 0; i < generators.length(); i++) {
     Handle<JSFunction> fun(generators[i]->function());
 
-    MaybeRecompileFunctionForDebugging(fun);
+    EnsureFunctionHasDebugBreakSlots(fun);
 
     int code_offset = generators[i]->continuation();
     int pc_offset = ComputePcOffsetFromCodeOffset(fun->code(), code_offset);
@@ -2217,7 +2224,7 @@ void Debug::PrepareForBreakPoints() {
       if (!shared->allows_lazy_compilation()) continue;
       if (shared->code()->kind() == Code::BUILTIN) continue;
 
-      MaybeRecompileFunctionForDebugging(function);
+      EnsureFunctionHasDebugBreakSlots(function);
     }
 
     RedirectActivationsToRecompiledCodeOnThread(isolate_,

src/debug.h

@@ -511,7 +511,7 @@ class Debug {
   Handle<Object> CheckBreakPoints(Handle<Object> break_point);
   bool CheckBreakPoint(Handle<Object> break_point_object);
 
-  void MaybeRecompileFunctionForDebugging(Handle<JSFunction> function);
+  void EnsureFunctionHasDebugBreakSlots(Handle<JSFunction> function);
   void RecompileAndRelocateSuspendedGenerators(
       const List<Handle<JSGeneratorObject> > &suspended_generators);