Use libc++ variant of string view and remove the FML variant.

ci/licenses_golden/licenses_flutter

@@ -186,9 +186,6 @@ FILE: ../../../flutter/fml/platform/win/native_library_win.cc
 FILE: ../../../flutter/fml/platform/win/paths_win.cc
 FILE: ../../../flutter/fml/platform/win/wstring_conversion.h
 FILE: ../../../flutter/fml/size.h
-FILE: ../../../flutter/fml/string_view.cc
-FILE: ../../../flutter/fml/string_view.h
-FILE: ../../../flutter/fml/string_view_unittest.cc
 FILE: ../../../flutter/fml/synchronization/atomic_object.h
 FILE: ../../../flutter/fml/synchronization/count_down_latch.cc
 FILE: ../../../flutter/fml/synchronization/count_down_latch.h

fml/BUILD.gn

@@ -52,8 +52,6 @@ source_set("fml") {
     "paths.cc",
     "paths.h",
     "size.h",
-    "string_view.cc",
-    "string_view.h",
     "synchronization/atomic_object.h",
     "synchronization/count_down_latch.cc",
     "synchronization/count_down_latch.h",
@@ -206,7 +204,6 @@ executable("fml_unittests") {
     "message_unittests.cc",
     "paths_unittests.cc",
     "platform/darwin/string_range_sanitization_unittests.mm",
-    "string_view_unittest.cc",
     "synchronization/count_down_latch_unittests.cc",
     "synchronization/semaphore_unittest.cc",
     "synchronization/thread_annotations_unittest.cc",

fml/base32.cc

@@ -5,14 +5,13 @@
 #include "flutter/fml/base32.h"
 
 #include <limits>
-
-#include "flutter/fml/macros.h"
+#include <string>
 
 namespace fml {
 
 static constexpr char kEncoding[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
 
-std::pair<bool, std::string> Base32Encode(StringView input) {
+std::pair<bool, std::string> Base32Encode(std::string_view input) {
   if (input.empty()) {
     return {true, ""};
   }

fml/base32.h

@@ -5,14 +5,12 @@
 #ifndef FLUTTER_FML_BASE32_H_
 #define FLUTTER_FML_BASE32_H_
 
-#include <string>
+#include <string_view>
 #include <utility>
 
-#include "flutter/fml/string_view.h"
-
 namespace fml {
 
-std::pair<bool, std::string> Base32Encode(StringView input);
+std::pair<bool, std::string> Base32Encode(std::string_view input);
 
 }  // namespace fml
 

fml/command_line.cc

@@ -36,26 +36,27 @@ CommandLine& CommandLine::operator=(const CommandLine& from) = default;
 
 CommandLine& CommandLine::operator=(CommandLine&& from) = default;
 
-bool CommandLine::HasOption(StringView name, size_t* index) const {
-  auto it = option_index_.find(name.ToString());
+bool CommandLine::HasOption(std::string_view name, size_t* index) const {
+  auto it = option_index_.find(name.data());
   if (it == option_index_.end())
     return false;
   if (index)
     *index = it->second;
   return true;
 }
 
-bool CommandLine::GetOptionValue(StringView name, std::string* value) const {
+bool CommandLine::GetOptionValue(std::string_view name,
+                                 std::string* value) const {
   size_t index;
   if (!HasOption(name, &index))
     return false;
   *value = options_[index].value;
   return true;
 }
 
-std::vector<fml::StringView> CommandLine::GetOptionValues(
-    StringView name) const {
-  std::vector<fml::StringView> ret;
+std::vector<std::string_view> CommandLine::GetOptionValues(
+    std::string_view name) const {
+  std::vector<std::string_view> ret;
   for (const auto& option : options_) {
     if (option.name == name)
       ret.push_back(option.value);
@@ -64,11 +65,11 @@ std::vector<fml::StringView> CommandLine::GetOptionValues(
 }
 
 std::string CommandLine::GetOptionValueWithDefault(
-    StringView name,
-    StringView default_value) const {
+    std::string_view name,
+    std::string_view default_value) const {
   size_t index;
   if (!HasOption(name, &index))
-    return default_value.ToString();
+    return {default_value.data(), default_value.size()};
   return options_[index].value;
 }
 

fml/command_line.h

@@ -40,11 +40,11 @@
 
 #include <initializer_list>
 #include <string>
+#include <string_view>
 #include <unordered_map>
 #include <vector>
 
 #include "flutter/fml/macros.h"
-#include "flutter/fml/string_view.h"
 
 namespace fml {
 
@@ -108,21 +108,21 @@ class CommandLine final {
   // Returns true if this command line has the option |name| (and if |index| is
   // non-null, sets |*index| to the index of the *last* occurrence of the given
   // option in |options()|) and false if not.
-  bool HasOption(StringView name, size_t* index = nullptr) const;
+  bool HasOption(std::string_view name, size_t* index = nullptr) const;
 
   // Gets the value of the option |name|. Returns true (and sets |*value|) on
   // success and false (leaving |*value| alone) on failure.
-  bool GetOptionValue(StringView name, std::string* value) const;
+  bool GetOptionValue(std::string_view name, std::string* value) const;
 
   // Gets all values of the option |name|. Returns all values, which may be
   // empty if the option is not specified.
-  std::vector<StringView> GetOptionValues(StringView name) const;
+  std::vector<std::string_view> GetOptionValues(std::string_view name) const;
 
   // Gets the value of the option |name|, with a default if the option is not
   // specified. (Note: This doesn't return a const reference, since this would
   // make the |default_value| argument inconvenient/dangerous.)
-  std::string GetOptionValueWithDefault(StringView name,
-                                        StringView default_value) const;
+  std::string GetOptionValueWithDefault(std::string_view name,
+                                        std::string_view default_value) const;
 
  private:
   bool has_argv0_ = false;

fml/command_line_unittest.cc

@@ -4,6 +4,7 @@
 
 #include "flutter/fml/command_line.h"
 
+#include <string_view>
 #include <utility>
 
 #include "flutter/fml/macros.h"
@@ -315,7 +316,7 @@ TEST(CommandLineTest, MultipleOccurrencesOfOption) {
       CommandLine::Option("flag1", "value3")};
   EXPECT_EQ("value3", cl.GetOptionValueWithDefault("flag1", "nope"));
   EXPECT_EQ("value2", cl.GetOptionValueWithDefault("flag2", "nope"));
-  std::vector<StringView> values = cl.GetOptionValues("flag1");
+  std::vector<std::string_view> values = cl.GetOptionValues("flag1");
   ASSERT_EQ(2u, values.size());
   EXPECT_EQ("value1", values[0]);
   EXPECT_EQ("value3", values[1]);