Enhance AudioSplicer to crossfade marked splice frames.

media/base/vector_math.cc

Index: media/base/vector_math.cc
diff --git a/media/base/vector_math.cc b/media/base/vector_math.cc
index 32584f5cf64ad2a1ecf400cbccd8f9341851cfa4..eec3f652da6d358ba8ab01955fc8958052776f0c 100644
--- a/media/base/vector_math.cc
+++ b/media/base/vector_math.cc
@@ -202,5 +202,14 @@ std::pair<float, float> EWMAAndMaxPower_NEON(
 }
 #endif
 
+
+// TODO(dalecurtis): Add SIMD versions and performance tests.
+void Crossfade(const float src[], int len, float dest[]) {
+  float cf_ratio = 0;
+  const float cf_increment = 1.0f / len;
+  for (int i = 0; i < len; ++i, cf_ratio += cf_increment)
+    dest[i] = (1.0f - cf_ratio) * src[i] + cf_ratio * dest[i];
+}
+
 }  // namespace vector_math
 }  // namespace media