Migrate most uses of Isolate::current_zone to Thread::zone.

runtime/vm/debugger_test.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/dart_api_impl.h"
 #include "vm/debugger.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
 // Search for the formatted string in buffer.
 //
 // TODO(turnidge): This function obscures the line number of failing
 // EXPECTs.  Rework this.
 static void ExpectSubstringF(const char* buff, const char* fmt, ...) {
-  Isolate* isolate = Isolate::Current();
-
   va_list args;
   va_start(args, fmt);
   intptr_t len = OS::VSNPrint(NULL, 0, fmt, args);
   va_end(args);
 
-  char* buffer = isolate->current_zone()->Alloc<char>(len + 1);
+  char* buffer = Thread::Current()->zone()->Alloc<char>(len + 1);
   va_list args2;
   va_start(args2, fmt);
   OS::VSNPrint(buffer, (len + 1), fmt, args2);
   va_end(args2);
 
   EXPECT_SUBSTRING(buffer, buff);
 }
 
 
 TEST_CASE(Debugger_PrintBreakpointsToJSONArray) {
@@ skipping 97 matching lines @@
   debugger->SetBreakpointAtLine(url, 2);
   Dart_Handle result = Dart_Invoke(lib, NewString("main"), 0, NULL);
   EXPECT_VALID(result);
   EXPECT(Dart_IsString(result));
 
   // We ran the code in InspectPausedEvent.
   EXPECT(saw_paused_event);
 }
 
 }  // namespace dart