Fix some more shorten-64-to-32 warnings:

runtime/vm/profiler.h

 // 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.
 
 #ifndef VM_PROFILER_H_
 #define VM_PROFILER_H_
 
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/code_observers.h"
@@ skipping 322 matching lines @@
   enum StateBits {
     kHeadSampleBit = 0,
     kLeafFrameIsDartBit = 1,
     kIgnoreBit = 2,
     kExitFrameBit = 3,
     kMissingFrameInsertedBit = 4,
     kTruncatedTraceBit = 5,
     kClassAllocationSampleBit = 6,
     kContinuationSampleBit = 7,
   };
-  class HeadSampleBit : public BitField<bool, kHeadSampleBit, 1> {};
-  class LeafFrameIsDart : public BitField<bool, kLeafFrameIsDartBit, 1> {};
-  class IgnoreBit : public BitField<bool, kIgnoreBit, 1> {};
-  class ExitFrameBit : public BitField<bool, kExitFrameBit, 1> {};
+  class HeadSampleBit : public BitField<uword, bool, kHeadSampleBit, 1> {};
+  class LeafFrameIsDart :
+      public BitField<uword, bool, kLeafFrameIsDartBit, 1> {};
+  class IgnoreBit : public BitField<uword, bool, kIgnoreBit, 1> {};
+  class ExitFrameBit : public BitField<uword, bool, kExitFrameBit, 1> {};
   class MissingFrameInsertedBit
-      : public BitField<bool, kMissingFrameInsertedBit, 1> {};
-  class TruncatedTraceBit : public BitField<bool, kTruncatedTraceBit, 1> {};
+      : public BitField<uword, bool, kMissingFrameInsertedBit, 1> {};
+  class TruncatedTraceBit :
+      public BitField<uword, bool, kTruncatedTraceBit, 1> {};
   class ClassAllocationSampleBit
-      : public BitField<bool, kClassAllocationSampleBit, 1> {};
+      : public BitField<uword, bool, kClassAllocationSampleBit, 1> {};
   class ContinuationSampleBit
-      : public BitField<bool, kContinuationSampleBit, 1> {};
+      : public BitField<uword, bool, kContinuationSampleBit, 1> {};
 
   int64_t timestamp_;
   ThreadId tid_;
   Isolate* isolate_;
   uword pc_marker_;
   uword stack_buffer_[kStackBufferSizeInWords];
   uword vm_tag_;
   uword user_tag_;
   uword metadata_;
   uword lr_;
@@ skipping 268 matching lines @@
  private:
   ZoneGrowableArray<ProcessedSample*> samples_;
   CodeLookupTable* code_lookup_table_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessedSampleBuffer);
 };
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_H_