TabManager: Remove a redundant log line which produces excessive log.

chrome/browser/memory/tab_manager_delegate_chromeos.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/memory/tab_manager_delegate_chromeos.h"
 
 #include <math.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 618 matching lines @@
       // The estimation is problematic since multiple tabs may share the same
       // process, while the calculation counts memory used by the whole process.
       // So |estimated_memory_freed_kb| is an over-estimation.
       int estimated_memory_freed_kb =
           mem_stat_->EstimatedMemoryFreedKB(it->tab()->renderer_handle);
       if (KillTab(tab_id)) {
         target_memory_to_free_kb -= estimated_memory_freed_kb;
         MemoryKillsMonitor::LogLowMemoryKill("TAB", estimated_memory_freed_kb);
         MEMORY_LOG(ERROR) << "Killed " << *it << ", estimated "
                           << estimated_memory_freed_kb << " KB freed";
-      } else {
-        MEMORY_LOG(ERROR) << "Failed to kill " << *it;

[Yusuke Sato, 2017/05/12 20:47:08]

What about changing this to VLOG? For debugging purposes, we might still want to
see it.

[cylee1, 2017/05/12 21:04:40]

Personally I don't think so. 
Particularly a tab is always in |candidates| no matter discarded or not. It
means for example there're 20 tabs and 10 of them are already discarded. For
each of following low memory event, those 10 tabs would still be scanned, each
producing a spam log line. 
For it to be informative, I think we should print the exact reason why it can't
be discarded (e.g., already discarded? active tab ? audio tab? etc). I think
it's not our priority at this stage.

       }
     }
   }
   if (target_memory_to_free_kb > 0) {
     MEMORY_LOG(ERROR)
         << "Unable to kill enough candidates to meet target_memory_to_free_kb ";
   }
 }
 
 void TabManagerDelegate::AdjustOomPrioritiesImpl(
@@ skipping 121 matching lines @@
     priority += priority_increment;
   }
 
   if (oom_scores_to_change.size()) {
     GetDebugDaemonClient()->SetOomScoreAdj(
         oom_scores_to_change, base::Bind(&OnSetOomScoreAdj));
   }
 }
 
 }  // namespace memory