DevTools: switch Timeline frontend into buffered mode and remove the corresponding experiment.

LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt

Index: LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt
diff --git a/LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt b/LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt
index d932518b727f68f924b670bab1f884c0299c5329..e589c10179c9f1cdc66d18b6d8822696d486ebb0 100644
--- a/LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt
+++ b/LayoutTests/inspector/timeline/timeline-decode-resize-expected.txt
@@ -42,18 +42,6 @@ DecodeImage Properties:
     children : <object>
     data : {
         backendNodeId : <number>
-        imageType : "JPEG"
-        url : .../inspector/timeline/resources/test.jpg
-    }
-    endTime : <number>
-    startTime : <number>
-    type : "DecodeImage"
-}
-DecodeImage Properties:
-{
-    children : <object>
-    data : {
-        backendNodeId : <number>
         imageType : "PNG"
         url : .../inspector/timeline/resources/test.png
     }
@@ -73,16 +61,4 @@ DecodeImage Properties:
     startTime : <number>
     type : "DecodeImage"
 }
-DecodeImage Properties:
-{
-    children : <object>
-    data : {
-        backendNodeId : <number>
-        imageType : "PNG"
-        url : .../inspector/timeline/resources/big.png
-    }
-    endTime : <number>
-    startTime : <number>
-    type : "DecodeImage"
-}