Remove legacy StartsWithASCII function.

This replaces it with base::StartsWith and the appropriate case flag. Since the existing version only ever did case-insensitive tests in ASCII, there should be no behavior change.

BUG=506255
TBR=jam

Review URL: https://codereview.chromium.org/1242023005

Cr-Original-Commit-Position: refs/heads/master@{#339175}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 955093110ad64d5ec6f5426991efaa4a680b5d6f
diff --git a/tools/gn/filesystem_utils.cc b/tools/gn/filesystem_utils.cc
index 42736c9..663e6ac 100644
--- a/tools/gn/filesystem_utils.cc
+++ b/tools/gn/filesystem_utils.cc
@@ -748,7 +748,8 @@
     const std::string& build_dir =
         settings->build_settings()->build_dir().value();
 
-    if (base::StartsWithASCII(source_dir.value(), build_dir, true)) {
+    if (base::StartsWith(source_dir.value(), build_dir,
+                         base::CompareCase::SENSITIVE)) {
       size_t build_dir_size = build_dir.size();
       result.value().append(&source_dir.value()[build_dir_size],
                             source_dir.value().size() - build_dir_size);
diff --git a/tools/gn/header_checker.cc b/tools/gn/header_checker.cc
index 1141e6e..b15b4fa 100644
--- a/tools/gn/header_checker.cc
+++ b/tools/gn/header_checker.cc
@@ -37,7 +37,8 @@
 SourceFile RemoveRootGenDirFromFile(const Target* target,
                                     const SourceFile& file) {
   const SourceDir& gen = target->settings()->toolchain_gen_dir();
-  if (!gen.is_null() && base::StartsWithASCII(file.value(), gen.value(), true))
+  if (!gen.is_null() && base::StartsWith(file.value(), gen.value(),
+                                         base::CompareCase::SENSITIVE))
     return SourceFile("//" + file.value().substr(gen.value().size()));
   return file;
 }
diff --git a/tools/gn/input_conversion.cc b/tools/gn/input_conversion.cc
index e4c20a0..fbde6f6 100644
--- a/tools/gn/input_conversion.cc
+++ b/tools/gn/input_conversion.cc
@@ -116,7 +116,8 @@
     return Value();  // Empty string means discard the result.
 
   const char kTrimPrefix[] = "trim ";
-  if (base::StartsWithASCII(input_conversion, kTrimPrefix, true)) {
+  if (base::StartsWith(input_conversion, kTrimPrefix,
+                       base::CompareCase::SENSITIVE)) {
     std::string trimmed;
     base::TrimWhitespaceASCII(input, base::TRIM_ALL, &trimmed);
 
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index a7a3d07..71488cb 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -219,7 +219,8 @@
     const Tool* tool = toolchain_->GetToolForTargetFinalOutput(this);
     if (tool) {
       // Only add the prefix if the name doesn't already have it.
-      if (!base::StartsWithASCII(name, tool->output_prefix(), true))
+      if (!base::StartsWith(name, tool->output_prefix(),
+                            base::CompareCase::SENSITIVE))
         result = tool->output_prefix();
     }
   }