Fix NiceValueToThreadPriority failing on an unknown nice value.

base/threading/platform_thread_internal_posix.cc

Index: base/threading/platform_thread_internal_posix.cc
diff --git a/base/threading/platform_thread_internal_posix.cc b/base/threading/platform_thread_internal_posix.cc
index 9af02044fceed2635b4fc5bf1ee5e1a06927a6fe..360ee113557d3cb2a6a276c71cd0b71979ba0e53 100644
--- a/base/threading/platform_thread_internal_posix.cc
+++ b/base/threading/platform_thread_internal_posix.cc
@@ -4,6 +4,7 @@
 
 #include "base/threading/platform_thread_internal_posix.h"
 
+#include <limits>
 #include "base/logging.h"

[gab, 2016/04/12 13:20:46]

nit: empty line between C++ includes and Chrome includes

[Yuta Kitamura, 2016/04/13 08:49:17]

Done.

 
 namespace base {
@@ -21,13 +22,23 @@ int ThreadPriorityToNiceValue(ThreadPriority priority) {
 }
 
 ThreadPriority NiceValueToThreadPriority(int nice_value) {
+  // Try to find a priority that best describes |nice_value|. If there isn't
+  // an exact match, this method returns the closest priority whose nice value
+  // is higher (lower priority) than |nice_value|.
+
+  ThreadPriority best_priority = ThreadPriority::BACKGROUND;
+  int best_nice_value = std::numeric_limits<int>::max();
   for (const ThreadPriorityToNiceValuePair& pair :

[danakj, 2016/04/12 21:02:26]

this should use const auto&

[Yuta Kitamura, 2016/04/13 08:49:17]

Done.

        kThreadPriorityToNiceValueMap) {

[danakj, 2016/04/12 21:02:26]

if you base::Reversed this to iterate opposite, you don't need to store a
best_priority, right? You just return the first one that is >= nice_value. If
you exit the loop without finding one you return background?

[Yuta Kitamura, 2016/04/13 08:49:17]

Yeah, that's much simpler. Thanks!

-    if (pair.nice_value == nice_value)
-      return pair.priority;
+    if (pair.nice_value >= nice_value) {
+      DCHECK_LT(pair.nice_value, best_nice_value);
+      best_priority = pair.priority;
+      best_nice_value = pair.nice_value;
+    } else {
+      break;
+    }
   }
-  NOTREACHED() << "Unknown nice value";
-  return ThreadPriority::NORMAL;
+  return best_priority;
 }
 
 }  // namespace internal