Move CHA state keeping from Isolate to Thread.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
===================================================================
--- runtime/vm/compiler.cc	(revision 44544)
+++ runtime/vm/compiler.cc	(working copy)
@@ -397,7 +397,7 @@
 
       // Class hierarchy analysis is registered with the isolate in the
       // constructor and unregisters itself upon destruction.
-      CHA cha(isolate);
+      CHA cha(thread);
 
       // TimerScope needs an isolate to be properly terminated in case of a
       // LongJump.
@@ -745,9 +745,9 @@
 
           // Register code with the classes it depends on because of CHA.
           for (intptr_t i = 0;
-               i < isolate->cha()->leaf_classes().length();
+               i < thread->cha()->leaf_classes().length();
                ++i) {
-            isolate->cha()->leaf_classes()[i]->RegisterCHACode(code);
+            thread->cha()->leaf_classes()[i]->RegisterCHACode(code);
           }
 
           for (intptr_t i = 0;