Replace scoped_ptr with unique_ptr in webrtc/common_audio/

(This is a re-land---without the real_fourier.h changes---of 11716, which was reverted in 11726.)

BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1731153002

Cr-Commit-Position: refs/heads/master@{#11742}
diff --git a/webrtc/common_audio/ring_buffer_unittest.cc b/webrtc/common_audio/ring_buffer_unittest.cc
index f8cce74..92c470a 100644
--- a/webrtc/common_audio/ring_buffer_unittest.cc
+++ b/webrtc/common_audio/ring_buffer_unittest.cc
@@ -12,10 +12,11 @@
 
 #include <stdlib.h>
 #include <time.h>
+
 #include <algorithm>
+#include <memory>
 
 #include "testing/gtest/include/gtest/gtest.h"
-#include "webrtc/base/scoped_ptr.h"
 
 namespace webrtc {
 
@@ -24,7 +25,7 @@
     WebRtc_FreeBuffer(ptr);
   }
 };
-typedef rtc::scoped_ptr<RingBuffer, FreeBufferDeleter> scoped_ring_buffer;
+typedef std::unique_ptr<RingBuffer, FreeBufferDeleter> scoped_ring_buffer;
 
 static void AssertElementEq(int expected, int actual) {
   ASSERT_EQ(expected, actual);
@@ -58,8 +59,8 @@
   srand(seed);
   for (int i = 0; i < kNumTests; i++) {
     const int buffer_size = std::max(rand() % kMaxBufferSize, 1);
-    rtc::scoped_ptr<int[]> write_data(new int[buffer_size]);
-    rtc::scoped_ptr<int[]> read_data(new int[buffer_size]);
+    std::unique_ptr<int[]> write_data(new int[buffer_size]);
+    std::unique_ptr<int[]> read_data(new int[buffer_size]);
     scoped_ring_buffer buffer(WebRtc_CreateBuffer(buffer_size, sizeof(int)));
     ASSERT_TRUE(buffer.get() != NULL);
     WebRtc_InitBuffer(buffer.get());