Reapply "Support for precise stepping in functions compiled before debugging was started (step 2)"

src/compiler.h

Index: src/compiler.h
diff --git a/src/compiler.h b/src/compiler.h
index 09aa23dec984f72b5644bd1f8e52855ffcda99d6..f99977aef4938a76cc9dbe867dc0bb47e09c31ed 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -120,6 +120,19 @@ class CompilationInfo BASE_EMBEDDED {
     ASSERT(IsOptimizing());
     osr_ast_id_ = osr_ast_id;
   }
+  void MarkCompilingForDebugging(Handle<Code> current_code) {
+    ASSERT(mode_ != OPTIMIZE);
+    ASSERT(current_code->kind() == Code::FUNCTION);
+    flags_ |= IsCompilingForDebugging::encode(true);
+    if (current_code->is_compiled_optimizable()) {
+      EnableDeoptimizationSupport();
+    } else {
+      mode_ = CompilationInfo::NONOPT;
+    }
+  }
+  bool IsCompilingForDebugging() {
+    return IsCompilingForDebugging::decode(flags_);
+  }
 
   bool has_global_object() const {
     return !closure().is_null() && (closure()->context()->global() != NULL);
@@ -139,10 +152,12 @@ class CompilationInfo BASE_EMBEDDED {
   void DisableOptimization();
 
   // Deoptimization support.
-  bool HasDeoptimizationSupport() const { return supports_deoptimization_; }
+  bool HasDeoptimizationSupport() const {
+    return SupportsDeoptimization::decode(flags_);
+  }
   void EnableDeoptimizationSupport() {
     ASSERT(IsOptimizable());
-    supports_deoptimization_ = true;
+    flags_ |= SupportsDeoptimization::encode(true);
   }
 
   // Determine whether or not we can adaptively optimize.
@@ -203,6 +218,11 @@ class CompilationInfo BASE_EMBEDDED {
   class IsNativesSyntaxAllowed: public BitField<bool, 5, 1> {};
   // Is this a function from our natives.
   class IsNative: public BitField<bool, 6, 1> {};
+  // Is this code being compiled with support for deoptimization..
+  class SupportsDeoptimization: public BitField<bool, 7, 1> {};
+  // If compiling for debugging produce just full code matching the
+  // initial mode setting.
+  class IsCompilingForDebugging: public BitField<bool, 8, 1> {};
 
 
   unsigned flags_;
@@ -231,7 +251,6 @@ class CompilationInfo BASE_EMBEDDED {
 
   // Compilation mode flag and whether deoptimization is allowed.
   Mode mode_;
-  bool supports_deoptimization_;
   int osr_ast_id_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilationInfo);