Add support for partial append window end trimming.

media/base/audio_discard_helper_unittest.cc

Index: media/base/audio_discard_helper_unittest.cc
diff --git a/media/base/audio_discard_helper_unittest.cc b/media/base/audio_discard_helper_unittest.cc
index 1ea0cc6f81657f2d63fcd0f59396448e86c35c65..3156c9a83930c4808808e917811a524be422b9a7 100644
--- a/media/base/audio_discard_helper_unittest.cc
+++ b/media/base/audio_discard_helper_unittest.cc
@@ -329,9 +329,14 @@ TEST(AudioDiscardHelperTest, InitialDiscardAndDiscardPaddingAndDecoderDelay) {
   ASSERT_FALSE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
   ASSERT_TRUE(discard_helper.initialized());
 
-  // Processing another buffer (with the same discard padding) should discard
-  // the back half of the buffer since kDecoderDelay is half a buffer.
+  // Processing another buffer should discard the back half of the buffer since
+  // kDecoderDelay is half a buffer.  The end padding should not be discarded
+  // until another buffer is processed.  kDuration / 4 is chosen for the end
+  // discard since it will force the end discard to start after position zero
+  // within the next decoded buffer.
   encoded_buffer->set_timestamp(kTimestamp + kDuration);
+  encoded_buffer->set_discard_padding(
+      std::make_pair(kDuration / 2, kDuration / 4));
   decoded_buffer = CreateDecodedBuffer(kTestFrames);
   ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
   ASSERT_NEAR(kDecoderDelay * kDataStep,
@@ -344,6 +349,37 @@ TEST(AudioDiscardHelperTest, InitialDiscardAndDiscardPaddingAndDecoderDelay) {
 
   // Verify it was actually the latter half of the buffer that was removed.
   ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+
+  // Verify the end discard padding is carried over to the next buffer.  Use
+  // kDuration / 2 so that the next buffer has its start entirely discarded.
+  encoded_buffer->set_timestamp(kTimestamp + kDuration);
+  encoded_buffer->set_discard_padding(
+      std::make_pair(base::TimeDelta(), kDuration / 2));
+  decoded_buffer = CreateDecodedBuffer(kTestFrames);
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  EXPECT_EQ(kTimestamp + kDuration / 2, decoded_buffer->timestamp());
+  EXPECT_EQ(3 * kDuration / 4, decoded_buffer->duration());
+  EXPECT_EQ(3 * kTestFrames / 4, decoded_buffer->frame_count());
+
+  // Verify it was actually the second quarter of the buffer that was removed.
+  const int kDiscardFrames = kTestFrames / 4;
+  ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+  ASSERT_FLOAT_EQ(
+      kDiscardFrames * 2 * kDataStep,
+      ExtractDecodedData(decoded_buffer, kDecoderDelay - kDiscardFrames));
+
+  // One last test to ensure carryover discard from the start works.
+  encoded_buffer->set_timestamp(kTimestamp + kDuration * 2);
+  encoded_buffer->set_discard_padding(DecoderBuffer::DiscardPadding());
+  decoded_buffer = CreateDecodedBuffer(kTestFrames);
+  ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  EXPECT_EQ(kTimestamp + kDuration / 2 + 3 * kDuration / 4,
+            decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+  ASSERT_FLOAT_EQ(kTestFrames / 2 * kDataStep,
+                  ExtractDecodedData(decoded_buffer, 0));
 }
 
 TEST(AudioDiscardHelperTest, DelayedDiscardInitialDiscardAndDiscardPadding) {