Temporary fix for a crash at TouchActionFilter::ReportTouchAction

This is a temporary fix to ensure that there will be no crash at
TouchActionFilter::ReportTouchAction when the |scrolling_touch_action_|
has no value.

TBR=nzolghadr@chromium.org

Bug: 879511
Change-Id: I007efc418c6169bc4ca91e9ac3d8e1627a8f2a4c
Reviewed-on: https://chromium-review.googlesource.com/1226823Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591397}

content/browser/renderer_host/input/touch_action_filter.cc

@@ -269,9 +269,12 @@ void TouchActionFilter::ReportTouchAction() {
   // Since |cc::kTouchActionAuto| is equivalent to |cc::kTouchActionMax|, we
   // must add one to the upper bound to be able to visualize the number of
   // times |cc::kTouchActionAuto| is hit.
-  UMA_HISTOGRAM_ENUMERATION("TouchAction.EffectiveTouchAction",
-                            scrolling_touch_action_.value(),
-                            cc::kTouchActionMax + 1);
+  // https://crbug.com/879511, remove this temporary fix.
+  if (scrolling_touch_action_.has_value()) {
+    UMA_HISTOGRAM_ENUMERATION("TouchAction.EffectiveTouchAction",
+                              scrolling_touch_action_.value(),
+                              cc::kTouchActionMax + 1);
+  }
 
   // Report how often the effective touch action computed by blink is or is
   // not equivalent to the whitelisted touch action computed by the