Add Pickle::Read/WriteUint64.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/297011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30320 0039d316-1c4b-4281-b951-d872f2087c98

diff --git a/base/pickle.cc b/base/pickle.cc
index 0be89c2..be76cf5a 100644
--- a/base/pickle.cc
+++ b/base/pickle.cc

@@ -6,8 +6,8 @@
 
 #include <stdlib.h>
 
+#include <algorithm>  // for max()
 #include <limits>
-#include <string>
 
 //------------------------------------------------------------------------------
 
@@ -181,6 +181,20 @@
   return true;
 }
 
+bool Pickle::ReadUInt64(void** iter, uint64* result) const {
+  DCHECK(iter);
+  if (!*iter)
+    *iter = const_cast<char*>(payload());
+
+  if (!IteratorHasRoomFor(*iter, sizeof(*result)))
+    return false;
+
+  memcpy(result, *iter, sizeof(*result));
+
+  UpdateIter(iter, sizeof(*result));
+  return true;
+}
+
 bool Pickle::ReadIntPtr(void** iter, intptr_t* result) const {
   DCHECK(iter);
   if (!*iter)
@@ -355,7 +369,7 @@
 }
 
 void Pickle::TrimWriteData(int new_length) {
-  DCHECK(variable_buffer_offset_ != 0);
+  DCHECK_NE(variable_buffer_offset_, 0);
 
   // Fetch the the variable buffer size
   int* cur_length = reinterpret_cast<int*>(