VM: Remove unnecesary load of isolate in some stubs.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 05d8d14635bb590b09914e57dc9fe40734efc756..b4534c9b535636401494231df15f31c768c1a64f 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -92,7 +92,6 @@ static void CheckOffsets() {
   // These offsets are embedded in precompiled instructions. We need simarm
   // (compiler) and arm (runtime) to agree.
   CHECK_OFFSET(Heap::TopOffset(Heap::kNew), 8);
-  CHECK_OFFSET(Isolate::heap_offset(), 8);
   CHECK_OFFSET(Thread::stack_limit_offset(), 4);
   CHECK_OFFSET(Thread::object_null_offset(), 36);
   CHECK_OFFSET(SingleTargetCache::upper_limit_offset(), 14);
@@ -102,7 +101,6 @@ static void CheckOffsets() {
   // These offsets are embedded in precompiled instructions. We need simmips
   // (compiler) and mips (runtime) to agree.
   CHECK_OFFSET(Heap::TopOffset(Heap::kNew), 8);
-  CHECK_OFFSET(Isolate::heap_offset(), 8);
   CHECK_OFFSET(Thread::stack_limit_offset(), 4);
   CHECK_OFFSET(Thread::object_null_offset(), 36);
   CHECK_OFFSET(SingleTargetCache::upper_limit_offset(), 14);
@@ -112,7 +110,6 @@ static void CheckOffsets() {
   // These offsets are embedded in precompiled instructions. We need simarm64
   // (compiler) and arm64 (runtime) to agree.
   CHECK_OFFSET(Heap::TopOffset(Heap::kNew), 8);
-  CHECK_OFFSET(Isolate::heap_offset(), 16);
   CHECK_OFFSET(Thread::stack_limit_offset(), 8);
   CHECK_OFFSET(Thread::object_null_offset(), 72);
   CHECK_OFFSET(SingleTargetCache::upper_limit_offset(), 28);