Fix for issue 14790 - Crash when using dartium devtools

runtime/vm/stack_frame_arm.h

Index: runtime/vm/stack_frame_arm.h
===================================================================
--- runtime/vm/stack_frame_arm.h	(revision 30084)
+++ runtime/vm/stack_frame_arm.h	(working copy)
@@ -16,19 +16,24 @@
                | saved LR           |    (PC of current frame)
                | callee's PC marker |
                +--------------------+
-Current frame  | ...                | <- SP of current frame
-               | first local        |
-               | caller's PP        |
+Current frame  | ...               T| <- SP of current frame
+               | first local       T|
+               | caller's PP       T|
                | caller's FP        | <- FP of current frame
                | caller's LR        |    (PC of caller frame)
                | PC marker          |    (current frame's code entry + offset)
                +--------------------+
 Caller frame   | last parameter     | <- SP of caller frame
                |  ...               |
+
+               T against a slot indicates it needs to be traversed during GC.
 */
 
 static const int kDartFrameFixedSize = 4;  // PP, FP, LR, PC marker.
 static const int kSavedPcSlotFromSp = -2;
+
+static const int kFirstObjectSlotFromFp = -2;  // Used by GC to traverse stack.
+
 static const int kFirstLocalSlotFromFp = -2;
 static const int kSavedCallerPpSlotFromFp = -1;
 static const int kSavedCallerFpSlotFromFp = 0;
@@ -44,4 +49,3 @@
 }  // namespace dart
 
 #endif  // VM_STACK_FRAME_ARM_H_
-