Fully qualify googletest symbols.

Semi-automatically created with:

git grep -l " testing::" | xargs sed -i "s/ testing::/ ::testing::/g"
git grep -l "(testing::" | xargs sed -i "s/(testing::/(::testing::/g"
git cl format

After this, two .cc files failed to compile and I have fixed them
manually.

Bug: webrtc:10523
Change-Id: I4741d3bcedc831b6c5fdc04485678617eb4ce031
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132018
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27526}
diff --git a/modules/audio_processing/include/mock_audio_processing.h b/modules/audio_processing/include/mock_audio_processing.h
index 7504b51..141a8ac 100644
--- a/modules/audio_processing/include/mock_audio_processing.h
+++ b/modules/audio_processing/include/mock_audio_processing.h
@@ -103,13 +103,13 @@
   MOCK_CONST_METHOD0(frame_size_ms, int());
 };
 
-class MockAudioProcessing : public testing::NiceMock<AudioProcessing> {
+class MockAudioProcessing : public ::testing::NiceMock<AudioProcessing> {
  public:
   MockAudioProcessing()
-      : gain_control_(new testing::NiceMock<MockGainControl>()),
-        level_estimator_(new testing::NiceMock<MockLevelEstimator>()),
-        noise_suppression_(new testing::NiceMock<MockNoiseSuppression>()),
-        voice_detection_(new testing::NiceMock<MockVoiceDetection>()) {}
+      : gain_control_(new ::testing::NiceMock<MockGainControl>()),
+        level_estimator_(new ::testing::NiceMock<MockLevelEstimator>()),
+        noise_suppression_(new ::testing::NiceMock<MockNoiseSuppression>()),
+        voice_detection_(new ::testing::NiceMock<MockVoiceDetection>()) {}
 
   virtual ~MockAudioProcessing() {}