AppRTCDemo file logging.

Adds logging macros to log logs to a file. Undeletes CircularFileStream
for that purpose.

BUG=
R=jiayl@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1217473011 .

Cr-Commit-Position: refs/heads/master@{#9582}
diff --git a/talk/examples/objc/AppRTCDemo/common/ARDLogging.h b/talk/examples/objc/AppRTCDemo/common/ARDLogging.h
new file mode 100644
index 0000000..dfb31d8
--- /dev/null
+++ b/talk/examples/objc/AppRTCDemo/common/ARDLogging.h
@@ -0,0 +1,88 @@
+/*
+ * libjingle
+ * Copyright 2015 Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright notice,
+ *     this list of conditions and the following disclaimer in the documentation
+ *     and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#import <Foundation/Foundation.h>
+
+// We route all logging through the WebRTC logger. By doing this we will get
+// both app and WebRTC logs in the same place, which we can then route to a
+// file if we need to. A side effect of this is that we get severity for free.
+typedef NS_ENUM(NSInteger, ARDLogSeverity) {
+  kARDLogSeverityVerbose,
+  kARDLogSeverityInfo,
+  kARDLogSeverityWarning,
+  kARDLogSeverityError,
+};
+
+#if defined(__cplusplus)
+extern "C" void ARDLogToWebRTCLogger(ARDLogSeverity severity,
+                                     NSString *logString);
+extern "C" NSString *ARDFileName(const char *filePath);
+extern "C" void ARDLogInit();
+#else
+// Logs |logString| to the WebRTC logger at the given severity.
+extern void ARDLogToWebRTCLogger(ARDLogSeverity severity, NSString *logString);
+// Returns the filename with the path prefix removed.
+extern NSString *ARDFileName(const char *filePath);
+// Initializes the correct logging levels. This should be called once on app
+// startup.
+extern void ARDLogInit();
+#endif
+
+#define ARDLogString(format, ...)                    \
+  [NSString stringWithFormat:@"(%@:%d %s): " format, \
+      ARDFileName(__FILE__),                         \
+      __LINE__,                                      \
+      __FUNCTION__,                                  \
+      ##__VA_ARGS__]
+
+#define ARDLogEx(severity, format, ...)                        \
+  do {                                                         \
+    NSString *logString = ARDLogString(format, ##__VA_ARGS__); \
+    ARDLogToWebRTCLogger(severity, logString);                 \
+  } while (false)
+
+#define ARDLogVerbose(format, ...)                        \
+  ARDLogEx(kARDLogSeverityVerbose, format, ##__VA_ARGS__) \
+
+#define ARDLogInfo(format, ...)                           \
+  ARDLogEx(kARDLogSeverityInfo, format, ##__VA_ARGS__)    \
+
+#define ARDLogWarning(format, ...)                        \
+  ARDLogEx(kARDLogSeverityWarning, format, ##__VA_ARGS__) \
+
+#define ARDLogError(format, ...)                          \
+  ARDLogEx(kARDLogSeverityError, format, ##__VA_ARGS__)   \
+
+#ifdef _DEBUG
+#define ARDLogDebug(format, ...) ARDLogInfo(format, ##__VA_ARGS__)
+#else
+#define ARDLogDebug(format, ...) \
+  do {                           \
+  } while (false)
+#endif
+
+#define ARDLog(format, ...) ARDLogInfo(format, ##__VA_ARGS__)