Roll forward up to cl/353292511.

cpp/platform/base/BUILD

@@ -80,6 +80,28 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "cancellation_flag",
+    srcs = [
+        "cancellation_flag.cc",
+    ],
+    hdrs = [
+        "cancellation_flag.h",
+    ],
+    visibility = [
+        "//core/internal:__subpackages__",
+        "//platform/api:__subpackages__",
+        "//platform/impl:__subpackages__",
+        "//platform/public:__pkg__",
+    ],
+    deps = [
+        ":base",
+        ":util",
+        "//absl/container:flat_hash_set",
+        "//absl/synchronization",
+    ],
+)
+
 cc_library(
     name = "test_util",
     testonly = True,
@@ -129,6 +151,17 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "cancellation_flag_test",
+    srcs = [
+        "cancellation_flag_test.cc",
+    ],
+    deps = [
+        ":cancellation_flag",
+        "//testing/base/public:gunit_main",
+    ],
+)
+
 cc_with_non_compile_test(
     name = "exception_test",
     srcs = [

cpp/platform/base/cancellation_flag.cc

@@ -0,0 +1,32 @@
+#include "platform/base/cancellation_flag.h"
+
+namespace location {
+namespace nearby {
+
+CancellationFlag::CancellationFlag() {
+  mutex_ = std::make_unique<absl::Mutex>();
+}
+
+CancellationFlag::CancellationFlag(bool cancelled) {
+  mutex_ = std::make_unique<absl::Mutex>();
+  cancelled_ = cancelled;
+}
+
+void CancellationFlag::Cancel() {
+  absl::MutexLock lock(mutex_.get());
+
+  if (cancelled_) {
+    // Someone already cancelled. Return immediately.
+    return;
+  }
+  cancelled_ = true;
+}
+
+bool CancellationFlag::Cancelled() const {
+  absl::MutexLock lock(mutex_.get());
+
+  return cancelled_;
+}
+
+}  // namespace nearby
+}  // namespace location

cpp/platform/base/cancellation_flag.h

@@ -0,0 +1,37 @@
+#ifndef PLATFORM_BASE_CANCELLATION_FLAG_H_
+#define PLATFORM_BASE_CANCELLATION_FLAG_H_
+
+#include <memory>
+
+#include "absl/synchronization/mutex.h"
+
+namespace location {
+namespace nearby {
+
+// A cancellation flag to mark an operation has been cancelled and should be
+// cleaned up as soon as possible.
+class CancellationFlag {
+ public:
+  CancellationFlag();
+  explicit CancellationFlag(bool cancelled);
+  CancellationFlag(const CancellationFlag &) = delete;
+  CancellationFlag &operator=(const CancellationFlag &) = delete;
+  CancellationFlag(CancellationFlag &&) = default;
+  CancellationFlag &operator=(CancellationFlag &&) = default;
+  virtual ~CancellationFlag() = default;
+
+  // Set the flag as cancelled.
+  void Cancel() ABSL_LOCKS_EXCLUDED(mutex_);
+
+  // Returns true if the flag has been set to cancelled.
+  bool Cancelled() const ABSL_LOCKS_EXCLUDED(mutex_);
+
+ private:
+  std::unique_ptr<absl::Mutex> mutex_;
+  bool cancelled_ ABSL_GUARDED_BY(mutex_) = false;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_BASE_CANCELLATION_FLAG_H_

cpp/platform/base/cancellation_flag_test.cc

@@ -0,0 +1,20 @@
+#include "platform/base/cancellation_flag.h"
+
+#include "gtest/gtest.h"
+
+namespace location {
+namespace nearby {
+
+TEST(CancellationFlagTest, InitialValueIsFalse) {
+  CancellationFlag flag;
+  EXPECT_FALSE(flag.Cancelled());
+}
+
+TEST(CancellationFlagTest, CanCancel) {
+  CancellationFlag flag;
+  flag.Cancel();
+  EXPECT_TRUE(flag.Cancelled());
+}
+
+}  // namespace nearby
+}  // namespace location

cpp/platform/impl/g3/webrtc.h

@@ -27,7 +27,7 @@ class WebRtcSignalingMessenger : public api::WebRtcSignalingMessenger {
   void StopReceivingMessages() override;
 
  private:
-  absl::string_view self_id_;
+  std::string self_id_;
   connections::LocationHint location_hint_;
 };
 

cpp/platform/public/BUILD

@@ -38,7 +38,6 @@ cc_library(
         "//platform/base:logging",
         "//platform/base:util",
         "//absl/base:core_headers",
-        "//absl/container:flat_hash_map",
         "//absl/time",
     ],
 )