Introduce concurrent on-stack replacement.

src/full-codegen.h

Index: src/full-codegen.h
diff --git a/src/full-codegen.h b/src/full-codegen.h
index ed2cc179213add60d4808615f386f0da2f6ee0f3..d244740da903485c5fa7ad99b4bba9d5faebeeaf 100644
--- a/src/full-codegen.h
+++ b/src/full-codegen.h
@@ -141,7 +141,8 @@ class FullCodeGenerator: public AstVisitor {
 
   class BackEdgeTableIterator {
    public:
-    explicit BackEdgeTableIterator(Code* unoptimized) {
+    explicit BackEdgeTableIterator(Code* unoptimized,
+                                   DisallowHeapAllocation* required) {
       ASSERT(unoptimized->kind() == Code::FUNCTION);
       instruction_start_ = unoptimized->instruction_start();
       cursor_ = instruction_start_ + unoptimized->back_edge_table_offset();
@@ -181,6 +182,14 @@ class FullCodeGenerator: public AstVisitor {
 
     uint32_t table_length() { return table_length_; }
 
+    bool FindPcOffset(uint32_t target_pc_offset) {
+      while (!Done()) {
+        if (pc_offset() == target_pc_offset) return true;
+        Next();
+      }
+      return false;
+    }
+
    private:
     static const int kTableLengthSize = kIntSize;
     static const int kAstIdOffset = 0 * kIntSize;
@@ -192,7 +201,6 @@ class FullCodeGenerator: public AstVisitor {
     Address end_;
     Address instruction_start_;
     uint32_t table_length_;
-    DisallowHeapAllocation no_gc_while_iterating_over_raw_addresses_;
 
     DISALLOW_COPY_AND_ASSIGN(BackEdgeTableIterator);
   };