Replace media::Limits struct with media::limits namespace and update documentation.

content/renderer/media/rtc_video_decoder_unittest.cc

Index: content/renderer/media/rtc_video_decoder_unittest.cc
diff --git a/content/renderer/media/rtc_video_decoder_unittest.cc b/content/renderer/media/rtc_video_decoder_unittest.cc
index 903cfc308505230593792acb43601e783a2d3b51..73d2bb46ecf6487dcecde95179a0826e89f056f4 100644
--- a/content/renderer/media/rtc_video_decoder_unittest.cc
+++ b/content/renderer/media/rtc_video_decoder_unittest.cc
@@ -30,7 +30,6 @@ using ::testing::SetArgumentPointee;
 using ::testing::StrictMock;
 using ::testing::WithArg;
 using ::testing::Invoke;
-using media::Limits;
 using media::MockStatisticsCallback;
 using media::MockVideoRenderer;
 using media::MockFilterHost;
@@ -205,7 +204,7 @@ TEST_F(RTCVideoDecoderTest, DoRenderFrame) {
 
   NullVideoFrame video_frame;
 
-  for (size_t i = 0; i < Limits::kMaxVideoFrames; ++i) {
+  for (size_t i = 0; i < media::limits::kMaxVideoFrames; ++i) {
     decoder_->RenderFrame(&video_frame);
   }