Isolate/Thread split: Isolate -> Zone for LocationSummary.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
===================================================================
--- runtime/vm/flow_graph_compiler.cc	(revision 42919)
+++ runtime/vm/flow_graph_compiler.cc	(working copy)
@@ -51,6 +51,9 @@
     "Enable inlining of SIMD related method calls.");
 DEFINE_FLAG(bool, source_lines, false, "Emit source line as assembly comment.");
 
+// Quick access to the locally defined isolate() method.
+#define I (isolate())
+
 // Assign locations to incoming arguments, i.e., values pushed above spill slots
 // with PushArgument.  Recursively allocates from outermost to innermost
 // environment.
@@ -1125,7 +1128,8 @@
 void FlowGraphCompiler::AllocateRegistersLocally(Instruction* instr) {
   ASSERT(!is_optimizing());
 
-  instr->InitializeLocationSummary(isolate(), false);  // Not optimizing.
+  instr->InitializeLocationSummary(I->current_zone(),
+                                   false);  // Not optimizing.
   LocationSummary* locs = instr->locs();
 
   bool blocked_registers[kNumberOfCpuRegisters];