Cleanup: Pass std::string as const reference from ios/

Passing std::string by reference can prevent extra copying of object.

BUG=367418
TEST=
R=droger@chromium.org,rohitrao@chromium.org

Review URL: https://codereview.chromium.org/1354353003

Cr-Commit-Position: refs/heads/master@{#349910}

5 files changed, 8 insertions, 8 deletions

diff --git a/ios/chrome/common/string_util.h b/ios/chrome/common/string_util.h
index b081321..b977c4b 100644
--- a/ios/chrome/common/string_util.h
+++ b/ios/chrome/common/string_util.h
@@ -27,7 +27,8 @@ NSCharacterSet* GraphicCharactersSet();
 NSString* CleanNSStringForDisplay(NSString* dirty, BOOL removeGraphicChars);
 
 // Cleans a std::string identically to CleanNSStringForDisplay()
-std::string CleanStringForDisplay(std::string dirty, BOOL removeGraphicChars);
+std::string CleanStringForDisplay(const std::string& dirty,
+                                  BOOL removeGraphicChars);
 
 // Find the longest leading substring of |string| that, when rendered with
 // |attributes|, will fit on a single line inside |targetWidth|. If |trailing|
diff --git a/ios/chrome/common/string_util.mm b/ios/chrome/common/string_util.mm
index d8fca0e..395f660 100644
--- a/ios/chrome/common/string_util.mm
+++ b/ios/chrome/common/string_util.mm
@@ -116,7 +116,8 @@ NSString* CleanNSStringForDisplay(NSString* dirty, BOOL removeGraphicChars) {
   return cleanString;
 }
 
-std::string CleanStringForDisplay(std::string dirty, BOOL removeGraphicChars) {
+std::string CleanStringForDisplay(const std::string& dirty,
+                                  BOOL removeGraphicChars) {
   return base::SysNSStringToUTF8(CleanNSStringForDisplay(
       base::SysUTF8ToNSString(dirty), removeGraphicChars));
 }
diff --git a/ios/crnet/crnet_environment.h b/ios/crnet/crnet_environment.h
index b007fbb..71afb17 100644
--- a/ios/crnet/crnet_environment.h
+++ b/ios/crnet/crnet_environment.h
@@ -36,7 +36,7 @@ class CrNetEnvironment {
   static void Initialize();
 
   // |user_agent_product_name| will be used to generate the user-agent.
-  CrNetEnvironment(std::string user_agent_product_name);
+  CrNetEnvironment(const std::string& user_agent_product_name);
   ~CrNetEnvironment();
 
   // Installs this CrNet environment so requests are intercepted.
diff --git a/ios/crnet/crnet_environment.mm b/ios/crnet/crnet_environment.mm
index c8650cb..9fa39da 100644
--- a/ios/crnet/crnet_environment.mm
+++ b/ios/crnet/crnet_environment.mm
@@ -253,15 +253,13 @@ void CrNetEnvironment::CloseAllSpdySessionsInternal() {
   }
 }
 
-CrNetEnvironment::CrNetEnvironment(std::string user_agent_product_name)
+CrNetEnvironment::CrNetEnvironment(const std::string& user_agent_product_name)
     : spdy_enabled_(false),
       quic_enabled_(false),
       sdch_enabled_(false),
       main_context_(new net::URLRequestContext),
       user_agent_product_name_(user_agent_product_name),
-      net_log_(new net::NetLog) {
-
-}
+      net_log_(new net::NetLog) {}
 
 void CrNetEnvironment::Install() {
   // Threads setup.
diff --git a/ios/web/navigation/crw_session_controller_unittest.mm b/ios/web/navigation/crw_session_controller_unittest.mm
index bd4e693..8a9171c 100644
--- a/ios/web/navigation/crw_session_controller_unittest.mm
+++ b/ios/web/navigation/crw_session_controller_unittest.mm
@@ -51,7 +51,7 @@ class CRWSessionControllerTest : public PlatformTest {
                                             browserState:&browser_state_]);
   }
 
-  web::Referrer MakeReferrer(std::string url) {
+  web::Referrer MakeReferrer(const std::string& url) {
     return web::Referrer(GURL(url), web::ReferrerPolicyDefault);
   }