Use a monotonic clock (TimeTicks) to report network times to WebCore.

base/time.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Time represents an absolute point in time, internally represented as
 // microseconds (s/1,000,000) since a platform-dependent epoch.  Each
 // platform's epoch, along with other system-dependent clock interface
 // routines, is defined in time_PLATFORM.cc.
 //
 // TimeDelta represents a duration of time, internally represented in
@@ skipping 446 matching lines @@
 
 // TimeTicks ------------------------------------------------------------------
 
 class BASE_EXPORT TimeTicks {
  public:
   TimeTicks() : ticks_(0) {
   }
 
   // Platform-dependent tick count representing "right now."
   // The resolution of this clock is ~1-15ms.  Resolution varies depending
-  // on hardware/operating system configuration.
+  // on hardware/operating system configuration.  The value should be the same
+  // across processes.

[wtc, 2011/08/29 21:59:41]

Nit: this comment is a little unclear.  You can perhaps say
that time origin (time 0) should be the same across processes,
and give the system boot time as an example of time 0.

The reason I asked to have darin or brettw look at this is
to ensure that this is a requirement that we can commit to.

   static TimeTicks Now();
 
   // Returns a platform-dependent high-resolution tick count. Implementation
   // is hardware dependent and may or may not return sub-millisecond
   // resolution.  THIS CALL IS GENERALLY MUCH MORE EXPENSIVE THAN Now() AND
   // SHOULD ONLY BE USED WHEN IT IS REALLY NEEDED.
   static TimeTicks HighResNow();
 
 #if defined(OS_WIN)
   // Get the absolute value of QPC time drift. For testing.
   static int64 GetQPCDriftMicroseconds();
 
   // Returns true if the high resolution clock is working on this system.
   // This is only for testing.
   static bool IsHighResClockWorking();
 #endif
 
   // Returns true if this object has not been initialized.
   bool is_null() const {
     return ticks_ == 0;
   }
 
   // Returns the internal numeric value of the TimeTicks object.
   int64 ToInternalValue() const {
     return ticks_;
   }
 
+  // Converts an integer value representing TimeTicks to a class. This is used
+  // when deserializing a |TimeTicks| structure, using a value that originated
+  // from |TimeTicks::ToInternalValue()|. It is not provided as a constructor
+  // because the integer type may be unclear from the perspective of a caller.
+  static TimeTicks FromInternalValue(int64 ticks) {
+    return TimeTicks(ticks);
+  }
+
   TimeTicks& operator=(TimeTicks other) {
     ticks_ = other.ticks_;
     return *this;
   }
 
   // Compute the difference between two times.
   TimeDelta operator-(TimeTicks other) const {
     return TimeDelta(ticks_ - other.ticks_);
   }
 
@@ skipping 52 matching lines @@
 #endif
 };
 
 inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
   return TimeTicks(t.ticks_ + delta_);
 }
 
 }  // namespace base
 
 #endif  // BASE_TIME_H_