Clean up InlineTextBoxPainter::PaintDocumentMarkers()

This CL consolidates two switch statements in this method and makes the code
easier to follow. It also removes NOTREACHED() from the switch statement to
allow adding painting code for a DocumentMarker in a separate CL from the
editing changes.

Bug: 
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ic125d633078ff3e74105f62ba64c5ebc349002bc
Reviewed-on: https://chromium-review.googlesource.com/592327Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Ryan Landay <rlanday@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491866}

third_party/WebKit/Source/core/paint/InlineTextBoxPainter.cpp

@@ -642,20 +642,6 @@ void InlineTextBoxPainter::PaintDocumentMarkers(
     DCHECK(*marker_it);
     const DocumentMarker& marker = **marker_it;
 
-    // Paint either the background markers or the foreground markers, but not
-    // both.
-    switch (marker.GetType()) {
-      case DocumentMarker::kGrammar:
-      case DocumentMarker::kSpelling:
-        if (marker_paint_phase == DocumentMarkerPaintPhase::kBackground)
-          continue;
-        break;
-      case DocumentMarker::kTextMatch:
-      case DocumentMarker::kComposition:
-      case DocumentMarker::kActiveSuggestion:
-        break;
-    }
-
     if (marker.EndOffset() <= inline_text_box_.Start()) {
       // marker is completely before this run.  This might be a marker that sits
       // before the first run we draw, or markers that were within runs we
@@ -670,10 +656,14 @@ void InlineTextBoxPainter::PaintDocumentMarkers(
     // marker intersects this run.  Paint it.
     switch (marker.GetType()) {
       case DocumentMarker::kSpelling:
+        if (marker_paint_phase == DocumentMarkerPaintPhase::kBackground)
+          continue;
         inline_text_box_.PaintDocumentMarker(paint_info.context, box_origin,
                                              marker, style, font, false);
         break;
       case DocumentMarker::kGrammar:
+        if (marker_paint_phase == DocumentMarkerPaintPhase::kBackground)
+          continue;
         inline_text_box_.PaintDocumentMarker(paint_info.context, box_origin,
                                              marker, style, font, true);
         break;
@@ -701,7 +691,8 @@ void InlineTextBoxPainter::PaintDocumentMarkers(
         }
       } break;
       default:
-        NOTREACHED();
+        // Marker is not painted, or painting code has not been added yet
+        break;
     }
   }
 }