Enables per-function far-branches for ARM and MIPS.

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 25620)
+++ runtime/vm/object.h	(working copy)
@@ -1635,6 +1635,11 @@
   }
   void set_is_intrinsic(bool value) const;
 
+  bool needs_far_branches() const {
+    return FarBranchesBit::decode(raw_ptr()->kind_tag_);
+  }
+  void set_needs_far_branches(bool value) const;
+
   bool HasOptimizedCode() const;
 
   // Returns true if the argument counts are valid for calling this function.
@@ -1787,7 +1792,8 @@
     kExternalBit = 7,
     kVisibleBit = 8,
     kIntrinsicBit = 9,
-    kKindTagBit = 10,
+    kNeedsFarBranchesBit = 10,
+    kKindTagBit = 11,
     kKindTagSize = 4,
   };
   class StaticBit : public BitField<bool, kStaticBit, 1> {};
@@ -1800,6 +1806,7 @@
   class ExternalBit : public BitField<bool, kExternalBit, 1> {};
   class VisibleBit : public BitField<bool, kVisibleBit, 1> {};
   class IntrinsicBit : public BitField<bool, kIntrinsicBit, 1> {};
+  class FarBranchesBit : public BitField<bool, kNeedsFarBranchesBit, 1> {};
   class KindBits :
     public BitField<RawFunction::Kind, kKindTagBit, kKindTagSize> {};  // NOLINT