base: Remove the string logging from CHECK().

ios/chrome/browser/ios_chrome_main_parts.mm

Index: ios/chrome/browser/ios_chrome_main_parts.mm
diff --git a/ios/chrome/browser/ios_chrome_main_parts.mm b/ios/chrome/browser/ios_chrome_main_parts.mm
index 722cad2bed9daa63425805ca552ac0badeaa4cec..c9da00a4e8d855157b9ee94a570d27f148d235ba 100644
--- a/ios/chrome/browser/ios_chrome_main_parts.mm
+++ b/ios/chrome/browser/ios_chrome_main_parts.mm
@@ -246,8 +246,7 @@ void IOSChromeMainParts::SetupFieldTrials() {
     bool result = base::FieldTrialList::CreateTrialsFromString(
         command_line->GetSwitchValueASCII(switches::kForceFieldTrials),
         std::set<std::string>());
-    CHECK(result) << "Invalid --" << switches::kForceFieldTrials
-                  << " list specified.";
+    CHECK(result);
   }
 
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
@@ -265,8 +264,7 @@ void IOSChromeMainParts::SetupFieldTrials() {
   bool result = http_header_provider->ForceVariationIds(
       command_line->GetSwitchValueASCII(switches::kIOSForceVariationIds),
       &variation_ids);
-  CHECK(result) << "Invalid list of variation ids specified (either in --"
-                << switches::kIOSForceVariationIds << " or in chrome://flags)";
+  CHECK(result);
 
   feature_list->InitializeFromCommandLine(
       command_line->GetSwitchValueASCII(switches::kEnableIOSFeatures),