Fix "unreachable code" warnings (MSVC warning 4702) in base/.

base/test/trace_event_analyzer.cc

Index: base/test/trace_event_analyzer.cc
===================================================================
--- base/test/trace_event_analyzer.cc	(revision 258102)
+++ base/test/trace_event_analyzer.cc	(working copy)
@@ -281,10 +281,8 @@
       return !left().Evaluate(event);
     default:
       NOTREACHED();
+      return false;
   }
-
-  NOTREACHED();
-  return false;
 }
 
 bool Query::CompareAsDouble(const TraceEvent& event, bool* result) const {
@@ -314,7 +312,6 @@
       NOTREACHED();
       return false;
   }
-  return true;
 }
 
 bool Query::CompareAsString(const TraceEvent& event, bool* result) const {
@@ -354,7 +351,6 @@
       NOTREACHED();
       return false;
   }
-  return true;
 }
 
 bool Query::EvaluateArithmeticOperator(const TraceEvent& event,
@@ -903,17 +899,11 @@
                 size_t position,
                 size_t* return_index) {
   DCHECK(return_index);
-  if (events.empty())
-    return false;
-  position = (position < events.size()) ? position : events.size() - 1;
-  for (;;) {
-    if (query.Evaluate(*events[position])) {
-      *return_index = position;
+  for (size_t i = std::min(position + 1, events.size()); i != 0; --i) {
+    if (query.Evaluate(*events[i - 1])) {
+      *return_index = i - 1;
       return true;
     }
-    if (position == 0)
-      return false;
-    --position;
   }
   return false;
 }