Reland "Refactor and remove media_optimization::MediaOptimization."

This reverts commit 6613f8e98ab3654ade7e8f5352d8d6711b157499.

Reason for revert: This change seemed innocent after all, so undoing speculative revert.

Original change's description:
> Revert "Refactor and remove media_optimization::MediaOptimization."
> 
> This reverts commit 07276e4f89a93b1479d7aeefa53b4fc32daf001b.
> 
> Reason for revert: Speculative revert due to downstream crashes.
> 
> Original change's description:
> > Refactor and remove media_optimization::MediaOptimization.
> > 
> > This CL removes MediaOptmization and folds some of its functionality
> > into VideoStreamEncoder.
> > 
> > The FPS tracking is now handled by a RateStatistics instance. Frame
> > dropping is still handled by FrameDropper. Both of these now live
> > directly in VideoStreamEncoder.
> > There is no intended change in behavior from this CL, but due to a new
> > way of measuring frame rate, some minor perf changes can be expected.
> > 
> > A small change in behavior is that OnBitrateUpdated is now called
> > directly rather than on the next frame. Since both encoding frame and
> > setting rate allocations happen on the encoder worker thread, there's
> > really no reason to cache bitrates and wait until the next frame.
> > An edge case though is that if a new bitrate is set before the first
> > frame, we must remember that bitrate and then apply it after the video
> > bitrate allocator has been first created.
> > 
> > In addition to existing unit tests, manual tests have been used to
> > confirm that frame dropping works as expected with misbehaving encoders.
> > 
> > Bug: webrtc:10164
> > Change-Id: I7ee9c8d3c4f2bcf23c8c420310b05a4d35d94744
> > Reviewed-on: https://webrtc-review.googlesource.com/c/115620
> > Commit-Queue: Erik Språng <sprang@webrtc.org>
> > Reviewed-by: Niels Moller <nisse@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#26147}
> 
> TBR=nisse@webrtc.org,sprang@webrtc.org
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: webrtc:10164
> Change-Id: Ie0dae19dd012bc09e793c9661a45823fd760c20c
> Reviewed-on: https://webrtc-review.googlesource.com/c/116780
> Reviewed-by: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#26191}

TBR=nisse@webrtc.org,sprang@webrtc.org

Change-Id: Ieda1fad301de002460bb0bf5a75267ea065176a8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:10164
Reviewed-on: https://webrtc-review.googlesource.com/c/116960
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26213}
diff --git a/modules/video_coding/video_sender_unittest.cc b/modules/video_coding/video_sender_unittest.cc
index 986bd3f..a9c9e45 100644
--- a/modules/video_coding/video_sender_unittest.cc
+++ b/modules/video_coding/video_sender_unittest.cc
@@ -319,14 +319,14 @@
               SetRateAllocation(new_rate_allocation, settings_.maxFramerate))
       .Times(1)
       .WillOnce(Return(0));
-  sender_->SetChannelParameters(new_bitrate_kbps * 1000, rate_allocator_.get(),
-                                nullptr);
+  sender_->SetChannelParameters(new_rate_allocation, settings_.maxFramerate);
   AddFrame();
   clock_.AdvanceTimeMilliseconds(kFrameIntervalMs);
 
   // Expect no call to encoder_.SetRates if the new bitrate is zero.
   EXPECT_CALL(encoder_, SetRateAllocation(_, _)).Times(0);
-  sender_->SetChannelParameters(0, rate_allocator_.get(), nullptr);
+  sender_->SetChannelParameters(VideoBitrateAllocation(),
+                                settings_.maxFramerate);
   AddFrame();
 }
 
@@ -363,8 +363,7 @@
   EXPECT_CALL(encoder_, SetRateAllocation(new_rate_allocation, _))
       .Times(1)
       .WillOnce(Return(0));
-  sender_->SetChannelParameters(new_bitrate_kbps * 1000, rate_allocator_.get(),
-                                nullptr);
+  sender_->SetChannelParameters(new_rate_allocation, settings_.maxFramerate);
 }
 
 TEST_F(TestVideoSenderWithMockEncoder,
@@ -375,8 +374,9 @@
   // Expect initial call to SetChannelParameters. Rates are initialized through
   // InitEncode and expects no additional call before the framerate (or bitrate)
   // updates.
-  sender_->SetChannelParameters(settings_.startBitrate * 1000,
-                                rate_allocator_.get(), nullptr);
+  sender_->SetChannelParameters(
+      rate_allocator_->GetAllocation(settings_.startBitrate * 1000, kInputFps),
+      kInputFps);
   while (clock_.TimeInMilliseconds() < start_time + kRateStatsWindowMs) {
     AddFrame();
     clock_.AdvanceTimeMilliseconds(1000 / kInputFps);
@@ -390,8 +390,7 @@
   EXPECT_CALL(encoder_, SetRateAllocation(new_rate_allocation, kInputFps))
       .Times(1)
       .WillOnce(Return(0));
-  sender_->SetChannelParameters(new_bitrate_bps, rate_allocator_.get(),
-                                nullptr);
+  sender_->SetChannelParameters(new_rate_allocation, kInputFps);
   AddFrame();
 }
 
@@ -439,12 +438,13 @@
       AddFrame();
       // SetChannelParameters needs to be called frequently to propagate
       // framerate from the media optimization into the encoder.
-      // Note: SetChannelParameters fails if less than 2 frames are in the
-      // buffer since it will fail to calculate the framerate.
+      const VideoBitrateAllocation bitrate_allocation =
+          rate_allocator_->GetAllocation(available_bitrate_kbps_ * 1000,
+                                         static_cast<uint32_t>(framerate));
       if (i != 0) {
-        EXPECT_EQ(VCM_OK, sender_->SetChannelParameters(
-                              available_bitrate_kbps_ * 1000,
-                              rate_allocator_.get(), nullptr));
+        EXPECT_EQ(VCM_OK,
+                  sender_->SetChannelParameters(
+                      bitrate_allocation, static_cast<uint32_t>(framerate)));
       }
     }
   }