Fix under-invalidation of media slider thumb when network state changes

third_party/WebKit/LayoutTests/paint/invalidation/video-mute-repaint-expected.txt

 {
   "name": "Content Root Layer",
   "bounds": [800, 600],
   "children": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "children": [
@@ skipping 12 matching lines @@
               "bounds": [700, 525],
               "drawsContent": true
             },
             {
               "name": "Squashing Layer (first squashed layer: LayoutFlexibleBox (relative positioned) DIV)",
               "position": [8, 8],
               "bounds": [700, 525],
               "drawsContent": true,
               "paintInvalidations": [
                 {
+                  "object": "LayoutBlockFlow DIV id='track'",
+                  "rect": [562, 485, 106, 48],
+                  "reason": "subtree"
+                },
+                {
                   "object": "LayoutFlexibleBox DIV",
                   "rect": [580, 508, 70, 2],
-                  "reason": "forced by layout"
+                  "reason": "subtree"
                 },
                 {
                   "object": "LayoutSlider INPUT",
                   "rect": [580, 508, 70, 2],
-                  "reason": "full"
+                  "reason": "subtree"
                 },
                 {
                   "object": "LayoutBlockFlow DIV id='thumb'",
                   "rect": [632, 485, 36, 48],
-                  "reason": "full"
+                  "reason": "subtree"
                 },
                 {
                   "object": "LayoutBlockFlow DIV id='thumb'",
                   "rect": [562, 485, 36, 48],
-                  "reason": "full"
+                  "reason": "subtree"
                 },
                 {
                   "object": "LayoutButton INPUT",
                   "rect": [530, 493, 32, 32],
-                  "reason": "full"
+                  "reason": "subtree"
                 }
               ]
             }
           ]
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutVideo VIDEO id='v'",
       "reason": "style change"
     },
     {
       "object": "LayoutButton INPUT",
-      "reason": "full"
+      "reason": "subtree"
     },
     {
       "object": "LayoutSlider INPUT",
-      "reason": "full"
+      "reason": "subtree"
     },
     {
       "object": "LayoutFlexibleBox DIV",
-      "reason": "forced by layout"
+      "reason": "subtree"
+    },
+    {
+      "object": "LayoutBlockFlow DIV id='track'",
+      "reason": "subtree"
     },
     {
       "object": "LayoutBlockFlow DIV id='thumb'",
-      "reason": "full"
+      "reason": "subtree"
     }
   ]
 }