Reland of place string::find(prefix) == 0 pattern with base::StartsWith().

chrome/browser/chromeos/profiles/profile_helper.cc

Index: chrome/browser/chromeos/profiles/profile_helper.cc
diff --git a/chrome/browser/chromeos/profiles/profile_helper.cc b/chrome/browser/chromeos/profiles/profile_helper.cc
index 08c4058c313c559c6f027ec55a996e65d74a9345..91ff48c42cd6d40251e1c900dc529c808b52e049 100644
--- a/chrome/browser/chromeos/profiles/profile_helper.cc
+++ b/chrome/browser/chromeos/profiles/profile_helper.cc
@@ -7,6 +7,7 @@
 #include "base/barrier_closure.h"
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/strings/string_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browsing_data/browsing_data_helper.h"
 #include "chrome/browser/browsing_data/browsing_data_remover.h"
@@ -138,13 +139,12 @@
 
   // Check that profile directory starts with the correct prefix.
   std::string prefix(chrome::kProfileDirPrefix);
-  if (profile_dir.find(prefix) != 0) {
+  if (!base::StartsWith(profile_dir, prefix, base::CompareCase::SENSITIVE)) {
     // This happens when creating a TestingProfile in browser tests.
     return std::string();
   }
 
-  return profile_dir.substr(prefix.length(),
-                            profile_dir.length() - prefix.length());
+  return profile_dir.substr(prefix.length());
 }
 
 // static