Add media perf benchamrk under network simulations.

tools/perf/page_sets/media_cns_cases.json

+{
+  "description": "Media benchmark on network constrained conditions.",
+  "media_metrics": {"action": "play-action"},
+  "add_browser_metrics": true,
+  "play-action": [
+    { "action": "play",
+      "wait_for_playing": true,
+      "wait_for_ended": true
+    }
+  ],
+  "pages": [
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_webm&src=tulip2.webm&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_webm&src=tulip2.webm&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_webm&src=tulip2.webm&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_ogv&src=tulip2.ogv&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_ogv&src=tulip2.ogv&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_ogv&src=tulip2.ogv&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_mp4&src=tulip2.mp4&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_mp4&src=tulip2.mp4&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_mp4&src=tulip2.mp4&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_wav&src=tulip2.wav&type=audio&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_wav&src=tulip2.wav&type=audio&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_wav&src=tulip2.wav&type=audio&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_ogg&src=tulip2.ogg&type=audio&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_ogg&src=tulip2.ogg&type=audio&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_ogg&src=tulip2.ogg&type=audio&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_mp3&src=tulip2.mp3&type=audio&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_mp3&src=tulip2.mp3&type=audio&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_mp3&src=tulip2.mp3&type=audio&net=wifi"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=no_constraints_m4a&src=tulip2.m4a&type=audio&net=none"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=cable_m4a&src=tulip2.m4a&type=audio&net=cable"
+    },
+    {
+      "url": "file://tough_video_cases/video.html?id=wifi_m4a&src=tulip2.m4a&type=audio&net=wifi"
+    }
+  ]
+}