Move LiveEdit-related code.

src/liveedit.h

Index: src/liveedit.h
diff --git a/src/liveedit.h b/src/liveedit.h
index b22d01ae4a2c8dbc6b13a4daccf9ac66f3aefe94..fed4b4d105320c4a9fe24986139f45265a9d1ffb 100644
--- a/src/liveedit.h
+++ b/src/liveedit.h
@@ -122,6 +122,63 @@ class LiveEdit : AllStatic {
   // of diff chunks.
   static Handle<JSArray> CompareStrings(Handle<String> s1,
                                         Handle<String> s2);
+
+  // Architecture-specific constant.
+  static const bool kFrameDropperSupported;
+
+  /**
+   * Defines layout of a stack frame that supports padding. This is a regular
+   * internal frame that has a flexible stack structure. LiveEdit can shift
+   * its lower part up the stack, taking up the 'padding' space when additional
+   * stack memory is required.
+   * Such frame is expected immediately above the topmost JavaScript frame.
+   *
+   * Stack Layout:
+   *   --- Top
+   *   LiveEdit routine frames
+   *   ---
+   *   C frames of debug handler
+   *   ---
+   *   ...
+   *   ---
+   *      An internal frame that has n padding words:
+   *      - any number of words as needed by code -- upper part of frame
+   *      - padding size: a Smi storing n -- current size of padding
+   *      - padding: n words filled with kPaddingValue in form of Smi
+   *      - 3 context/type words of a regular InternalFrame
+   *      - fp
+   *   ---
+   *      Topmost JavaScript frame
+   *   ---
+   *   ...
+   *   --- Bottom
+   */
+  // A size of frame base including fp. Padding words starts right above
+  // the base.
+  static const int kFrameDropperFrameSize = 4;
+  // A number of words that should be reserved on stack for the LiveEdit use.
+  // Stored on stack in form of Smi.
+  static const int kFramePaddingInitialSize = 1;
+  // A value that padding words are filled with (in form of Smi). Going
+  // bottom-top, the first word not having this value is a counter word.
+  static const int kFramePaddingValue = kFramePaddingInitialSize + 1;
+
+
+  // Describes how exactly a frame has been dropped from stack.
+  enum FrameDropMode {
+    // No frame has been dropped.
+    FRAMES_UNTOUCHED,
+    // The top JS frame had been calling IC stub. IC stub mustn't be called now.
+    FRAME_DROPPED_IN_IC_CALL,
+    // The top JS frame had been calling debug break slot stub. Patch the
+    // address this stub jumps to in the end.
+    FRAME_DROPPED_IN_DEBUG_SLOT_CALL,
+    // The top JS frame had been calling some C++ function. The return address
+    // gets patched automatically.
+    FRAME_DROPPED_IN_DIRECT_CALL,
+    FRAME_DROPPED_IN_RETURN_CALL,
+    CURRENTLY_SET_MODE
+  };
 };