- Handle doubles transferred in message snapshots specially.

runtime/vm/snapshot.h

Index: runtime/vm/snapshot.h
===================================================================
--- runtime/vm/snapshot.h	(revision 34679)
+++ runtime/vm/snapshot.h	(working copy)
@@ -182,6 +182,13 @@
     stream_.ReadBytes(addr, len);
   }
 
+  double ReadDouble() {
+    double result;
+    stream_.ReadBytes(reinterpret_cast<uint8_t*>(&result), sizeof(result));
+    return result;
+  }
+
+
   const uint8_t* CurrentBufferAddress() const {
     return stream_.AddressOfCurrentPosition();
   }
@@ -421,6 +428,10 @@
     stream_.WriteBytes(addr, len);
   }
 
+  void WriteDouble(double value) {
+    stream_.WriteBytes(reinterpret_cast<const uint8_t*>(&value), sizeof(value));
+  }
+
  protected:
   BaseWriter(uint8_t** buffer,
              ReAlloc alloc,