Add read-only mode to CommandLine that optimizes HasSwitch(const char*).

base/command_line.h

Index: base/command_line.h
diff --git a/base/command_line.h b/base/command_line.h
index 19df40c4c478bfa9befe59ad9eefc63f5b33c55f..cf298a0e163cebd926403012dc057912e21cff87 100644
--- a/base/command_line.h
+++ b/base/command_line.h
@@ -156,6 +156,9 @@ class BASE_EXPORT CommandLine {
 
   // Get a copy of all switches, along with their values.
   const SwitchMap& GetSwitches() const { return switches_; }
+  const std::vector<std::string>& GetSwitchVector() const {
+    return switch_vector_;
+  }
 
   // Append a switch [with optional value] to the command line.
   // Note: Switches will precede arguments regardless of appending order.
@@ -198,6 +201,9 @@ class BASE_EXPORT CommandLine {
   void ParseFromString(const base::string16& command_line);
 #endif
 
+  // Optimizes lookups into this CommandLine, but it can no longer be modified.
+  void MakeReadOnly();
+
  private:
   // Disallow default constructor; a program name must be explicitly specified.
   CommandLine();
@@ -214,6 +220,12 @@ class BASE_EXPORT CommandLine {
   // also quotes parts with '%' in them.
   StringType GetArgumentsStringInternal(bool quote_placeholders) const;
 
+  // Search for the switch in |switch_vector_|.
+  bool HasSwitchVector(const char string_constant[]) const;
+
+  // Search for the switch assuming the input is lowercase.
+  bool HasSwitchLowerCase(const char string_constant[]) const;
+
   // The singleton CommandLine representing the current process's command line.
   static CommandLine* current_process_commandline_;
 
@@ -225,6 +237,14 @@ class BASE_EXPORT CommandLine {
 
   // The index after the program and switches, any arguments start here.
   size_t begin_args_;
+
+  // A vector of switches. This allows looking up a const char* switch without
+  // allocating a string. It is initialized when this CommandLine is made
+  // read-only.
+  std::vector<std::string> switch_vector_;
+
+  // This is un-set when this CommandLine is made read-only.
+  bool writeable_;
 };
 
 }  // namespace base