Check rect under-invalidations

third_party/WebKit/LayoutTests/fast/repaint/resources/text-based-repaint.js

 // Asynchronous tests should manually call finishRepaintTest at the appropriate
 // time.
 window.testIsAsync = false;
 window.outputRepaintRects = true;
 window.generateMinimumRepaint = false; // See comments about 'Minimum repaint' below.
 
 // All repaint tests are asynchronous.
 if (window.testRunner)
     testRunner.waitUntilDone();
 
-if (window.internals)
+if (window.internals) {
     internals.settings.setUseDefaultImageInterpolationQuality(true);
+    // TODO(wangxianzhu): Some spv2 tests crash with under-invalidation-checking
+    // because the extra display items between Subsequence/EndSubsequence for
+    // under-invalidation checking breaks paint chunks. Should fix this when fixing
+    // crbug.com/596983.
+    if (!internals.runtimeFlags.slimmingPaintV2Enabled)
+        internals.runtimeFlags.slimmingPaintUnderInvalidationCheckingEnabled = true;
+}
 
 function runRepaintTest()
 {
     if (!window.testRunner || !window.internals) {
         setTimeout(repaintTest, 500);
         return;
     }
 
     if (window.enablePixelTesting)
         testRunner.dumpAsTextWithPixelResults();
@@ skipping 161 matching lines @@
             } else {
                 var newRect = [xBegin, y, xWidth, 1];
                 nextRectsMayContinue.push(newRect);
                 result.push(newRect);
             }
         }
         rectsMayContinue = nextRectsMayContinue;
     }
     return result;
 }