Use memmove instead of a loop to read bytes.

vm/snapshot.h

Index: vm/snapshot.h
===================================================================
--- vm/snapshot.h	(revision 8158)
+++ vm/snapshot.h	(working copy)
@@ -190,6 +190,12 @@
     return *current_++;
   }
 
+  void ReadBytes(uint8_t* addr, intptr_t len) {
+    ASSERT((current_ + len) < end_);
+    memmove(addr, current_, len);
+    current_ += len;
+  }
+
  private:
   const uint8_t* buffer_;
   const uint8_t* current_;
@@ -320,6 +326,10 @@
     return value;
   }
 
+  void ReadBytes(uint8_t* addr, intptr_t len) {
+    stream_.ReadBytes(addr, len);
+  }
+
   RawSmi* ReadAsSmi();
   intptr_t ReadSmiValue();