VM: New calling convention for generated code.

runtime/vm/stack_frame_x64.h

Index: runtime/vm/stack_frame_x64.h
diff --git a/runtime/vm/stack_frame_x64.h b/runtime/vm/stack_frame_x64.h
index 3d87d27767db47dc09815c7c0a12c13074674a6b..3ffd51fe05d69c008084c62a5800bdf461955d2d 100644
--- a/runtime/vm/stack_frame_x64.h
+++ b/runtime/vm/stack_frame_x64.h
@@ -19,7 +19,7 @@ Callee frame   | ...                |
 Current frame  | ...               T| <- RSP of current frame
                | first local       T|
                | caller's PP       T|
-               | PC marker          |    (current frame's code entry + offset)
+               | PC marker         T|    (current frame's code entry + offset)
                | caller's RBP       | <- RBP of current frame
                | caller's ret addr  |    (PC of caller frame)
                +--------------------+
@@ -32,7 +32,7 @@ Caller frame   | last parameter     | <- RSP of caller frame
 static const int kDartFrameFixedSize = 4;  // PC marker, RBP, PP, PC.
 static const int kSavedPcSlotFromSp = -1;
 
-static const int kFirstObjectSlotFromFp = -2;  // Used by GC to traverse stack.
+static const int kFirstObjectSlotFromFp = -1;  // Used by GC to traverse stack.
 
 static const int kFirstLocalSlotFromFp = -3;
 static const int kSavedCallerPpSlotFromFp = -2;