Use "\uFEFF" instead of "." in WebInspector.ViewportControl's gap elements.

third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js

Index: third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js b/third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js
index f1267fdb0aabc89492c21bdfa9f104a2831b86bb..ddb8a45fa8832a4ac66bf23f832ebf1435d421b1 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/ViewportControl.js
@@ -37,15 +37,18 @@ WebInspector.ViewportControl = function(provider)
     this.element = createElement("div");
     this.element.style.overflow = "auto";
     this._topGapElement = this.element.createChild("div");
-    this._topGapElement.textContent = ".";

[pfeldman, 2016/01/22 01:37:34]

lushnikov@ says that "." was here to render selection that spans beyond the
viewport prettier. and it seems it is no longer needed - either new selection
rendering helped or other things changed over time.

[skobes, 2016/01/22 01:51:53]

I first tried eliminating the text content but
inspector/console/console-viewport-selection.html failed.  I think the
range.intersectsNode calls in _updateSelectionModel depend on having non-empty
text content.

     this._topGapElement.style.height = "0px";

[pfeldman, 2016/01/22 01:37:34]

how come it contributes to the height? - it has zero height.

[skobes, 2016/01/22 01:51:53]

The text content produces overflow which contributes to the container's height. 
Example: https://jsbin.com/zisowo/edit?html,output

     this._topGapElement.style.color = "transparent";
     this._contentElement = this.element.createChild("div");
     this._bottomGapElement = this.element.createChild("div");
-    this._bottomGapElement.textContent = ".";
     this._bottomGapElement.style.height = "0px";
     this._bottomGapElement.style.color = "transparent";
 
+    // Text content needed for range intersection checks in _updateSelectionModel.
+    // Use Unicode ZERO WIDTH NO-BREAK SPACE, which avoids contributing any height to the element's layout overflow.
+    this._topGapElement.textContent = "\uFEFF";
+    this._bottomGapElement.textContent = "\uFEFF";
+
     this._provider = provider;
     this.element.addEventListener("scroll", this._onScroll.bind(this), false);
     this.element.addEventListener("copy", this._onCopy.bind(this), false);