Add UMA to measure time to open hyphenation dictionary

This patch adds UMA to measure time to open hyphenation dictionary.

The previous CL[1] added UMA that includes IPC as "Hyphenation.Open",
but this metric measures the time of the file task without the IPC.

[1] 2113933003

BUG=605840

Review-Url: https://codereview.chromium.org/2340613002
Cr-Commit-Position: refs/heads/master@{#418826}

content/browser/hyphenation/hyphenation_impl.cc

@@ -10,8 +10,10 @@
 
 #include "base/files/file.h"
 #include "base/files/file_path.h"
+#include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/timer/elapsed_timer.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "mojo/public/cpp/system/platform_handle.h"
 
@@ -43,7 +45,9 @@ static base::File& GetDictionaryFile(const std::string& locale) {
 #endif
   std::string filename = base::StringPrintf("hyph-%s.hyb", locale.c_str());
   base::FilePath path = dir.AppendASCII(filename);
+  base::ElapsedTimer timer;
   file.Initialize(path, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  UMA_HISTOGRAM_TIMES("Hyphenation.Open.File", timer.Elapsed());
   return file;
 }
 

tools/metrics/histograms/histograms.xml

@@ -19384,6 +19384,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>The time it takes to open a hyphenation dictionary.</summary>
 </histogram>
 
+<histogram name="Hyphenation.Open.File" units="ms">
+  <owner>kojii@chromium.org</owner>
+  <summary>The time it takes to open a hyphenation dictionary file.</summary>
+</histogram>
+
 <histogram name="Import.ImportedHistorySize.AutoImportFromIE" units="urls">
   <owner>gcomanici@chromium.org</owner>
   <summary>