Obj-C SDK Cleanup

This CL separates the files under sdk/objc into logical directories, replacing
the previous file layout under Framework/.

A long term goal is to have some system set up to generate the files under
sdk/objc/api (the PeerConnection API wrappers) from the C++ code. In the shorter
term the goal is to abstract out shared concepts from these classes in order to
make them as uniform as possible.

The separation into base/, components/, and helpers/ are to differentiate between
the base layer's common protocols, various utilities and the actual platform
specific components.

The old directory layout that resembled a framework's internal layout is not
necessary, since it is generated by the framework target when building it.

Bug: webrtc:9627
Change-Id: Ib084fd83f050ae980649ca99e841f4fb0580bd8f
Reviewed-on: https://webrtc-review.googlesource.com/94142
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24493}
diff --git a/sdk/objc/api/logging/RTCCallbackLogger.h b/sdk/objc/api/logging/RTCCallbackLogger.h
new file mode 100644
index 0000000..669f2a3
--- /dev/null
+++ b/sdk/objc/api/logging/RTCCallbackLogger.h
@@ -0,0 +1,35 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "RTCLogging.h"
+#import "RTCMacros.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+// This class intercepts WebRTC logs and forwards them to a registered block.
+// This class is not threadsafe.
+RTC_EXPORT
+@interface RTCCallbackLogger : NSObject
+
+// The severity level to capture. The default is kRTCLoggingSeverityInfo.
+@property(nonatomic, assign) RTCLoggingSeverity severity;
+
+// The callback will be called on the same thread that does the logging, so
+// if the logging callback can be slow it may be a good idea to implement
+// dispatching to some other queue.
+- (void)start:(nullable void (^)(NSString*))callback;
+
+- (void)stop;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/sdk/objc/api/logging/RTCCallbackLogger.mm b/sdk/objc/api/logging/RTCCallbackLogger.mm
new file mode 100644
index 0000000..8440d63
--- /dev/null
+++ b/sdk/objc/api/logging/RTCCallbackLogger.mm
@@ -0,0 +1,92 @@
+/*
+ *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "RTCCallbackLogger.h"
+
+#include <memory>
+
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/logsinks.h"
+
+class CallbackLogSink : public rtc::LogSink {
+ public:
+  CallbackLogSink(void (^callbackHandler)(NSString *message)) {
+    callback_handler_ = callbackHandler;
+  }
+
+  ~CallbackLogSink() override { callback_handler_ = nil; }
+
+  void OnLogMessage(const std::string &message) override {
+    if (callback_handler_) {
+      callback_handler_([NSString stringWithUTF8String:message.c_str()]);
+    }
+  }
+
+ private:
+  void (^callback_handler_)(NSString *message);
+};
+
+@implementation RTCCallbackLogger {
+  BOOL _hasStarted;
+  std::unique_ptr<CallbackLogSink> _logSink;
+}
+
+@synthesize severity = _severity;
+
+- (instancetype)init {
+  self = [super init];
+  if (self != nil) {
+    _severity = RTCLoggingSeverityInfo;
+  }
+  return self;
+}
+
+- (void)dealloc {
+  [self stop];
+}
+
+- (void)start:(nullable void (^)(NSString *))callback {
+  if (_hasStarted) {
+    return;
+  }
+
+  _logSink.reset(new CallbackLogSink(callback));
+
+  rtc::LogMessage::AddLogToStream(_logSink.get(), [self rtcSeverity]);
+  _hasStarted = YES;
+}
+
+- (void)stop {
+  if (!_hasStarted) {
+    return;
+  }
+  RTC_DCHECK(_logSink);
+  rtc::LogMessage::RemoveLogToStream(_logSink.get());
+  _hasStarted = NO;
+  _logSink.reset();
+}
+
+#pragma mark - Private
+
+- (rtc::LoggingSeverity)rtcSeverity {
+  switch (_severity) {
+    case RTCLoggingSeverityVerbose:
+      return rtc::LS_VERBOSE;
+    case RTCLoggingSeverityInfo:
+      return rtc::LS_INFO;
+    case RTCLoggingSeverityWarning:
+      return rtc::LS_WARNING;
+    case RTCLoggingSeverityError:
+      return rtc::LS_ERROR;
+  }
+}
+
+@end