Fix DateCache::DaylightSavingsOffsetInMs fallback path.

The code after the binary-search loop is unlikely to be reached,
but not actually UNREACHABLE(). Restore the "return 0" that was
there until a cleanup [1] removed it.

[1] crrev.com/c/507287/2/src/date.cc

Bug: chromium:767039
Change-Id: I9e007d3b7d693d4866ccc3e3cf2b71e78e9bd07f
Reviewed-on: https://chromium-review.googlesource.com/675755Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48117}

src/date.cc

@@ -310,7 +310,7 @@ int DateCache::DaylightSavingsOffsetInMs(int64_t time_ms) {
   }
 
   // Binary search for daylight savings offset change point,
-  // but give up if we don't find it in four iterations.
+  // but give up if we don't find it in five iterations.
   for (int i = 4; i >= 0; --i) {
     int delta = after_->start_sec - before_->end_sec;
     int middle_sec = (i == 0) ? time_sec : before_->end_sec + delta / 2;
@@ -332,7 +332,7 @@ int DateCache::DaylightSavingsOffsetInMs(int64_t time_ms) {
       }
     }
   }
-  UNREACHABLE();
+  return 0;
 }