Collecting encode_time_ms for each frame.

Also, in Sample struct, replacing double with the original type.
It makes more sense to save the original data as truthful as possible, and then
convert it to double later if necessary (in the plot script).

Review URL: https://codereview.webrtc.org/1374233002

Cr-Commit-Position: refs/heads/master@{#10184}

webrtc/video/full_stack_plot.py

@@ -34,15 +34,16 @@ import numpy
 
 # Fields
 DROPPED = 0
-INPUT_TIME = 1              # ms
-SEND_TIME = 2               # ms
-RECV_TIME = 3               # ms
-ENCODED_FRAME_SIZE = 4      # bytes
-PSNR = 5
-SSIM = 6
-RENDER_TIME = 7             # ms
+INPUT_TIME = 1              # ms (timestamp)
+SEND_TIME = 2               # ms (timestamp)
+RECV_TIME = 3               # ms (timestamp)
+RENDER_TIME = 4             # ms (timestamp)
+ENCODED_FRAME_SIZE = 5      # bytes
+PSNR = 6
+SSIM = 7
+ENCODE_TIME = 8             # ms (time interval)
 
-TOTAL_RAW_FIELDS = 8
+TOTAL_RAW_FIELDS = 9
 
 SENDER_TIME = TOTAL_RAW_FIELDS + 0
 RECEIVER_TIME = TOTAL_RAW_FIELDS + 1
@@ -66,6 +67,7 @@ _fields = [
     (PSNR, "psnr", "PSNR"),
     (SSIM, "ssim", "SSIM"),
     (RENDER_TIME, "render_time_ms", "render time"),
+    (ENCODE_TIME, "encode_time_ms", "encode time"),
     # Auto-generated
     (SENDER_TIME, "sender_time", "sender time"),
     (RECEIVER_TIME, "receiver_time", "receiver time"),