Makes GetBuildTime behave identically on all build types.

base/build_time.h

Index: base/build_time.h
diff --git a/base/build_time.h b/base/build_time.h
index 4f0abc381336641425dab76d4f1533a0041b22bb..603481ca004f99dc849aac2cf21bf2910f6c80d9 100644
--- a/base/build_time.h
+++ b/base/build_time.h
@@ -10,17 +10,15 @@
 
 namespace base {
 
-// GetBuildTime returns the time at which the current binary was built.
+// GetBuildTime returns the time at which the current binary was built,
+// rounded down to 5:00:00am at the start of the day in UTC.
 //
-// This uses the __DATE__ and __TIME__ macros, which don't trigger a rebuild
-// when they change. However, official builds will always be rebuilt from
-// scratch.
+// This uses a generated file, which doesn't trigger a rebuild when the time
+// changes. It will, however, be updated whenever //build/util/LASTCHANGE
+// changes.
 //
-// Also, since __TIME__ doesn't include a timezone, this value should only be
-// considered accurate to a day.
-//
-// NOTE: This function is disabled except for the official builds, by default
-// the date returned is "Sep 02 2008 08:00:00 PST".
+// This value should only be considered accurate to within a day.
+// It will always be in the past.

[Dirk Pranke, 2016/02/09 19:38:03]

This comment is wrong for non-official builds, since the date may be many days
older than the actual build date.

[M-A Ruel, 2016/02/09 19:47:41]

I agree, the comment is stale since the accuracy is dependent on OFFICIAL_BUILD.

[Zachary Forman, 2016/02/09 20:57:35]

Acknowledged and corrected.

 Time BASE_EXPORT GetBuildTime();
 
 }  // namespace base