Fix dgrid horizontal scroll on focus

When navigating with keyboard on a grid that is not wide enough to fit
the entire grid, ensure that the column is scrolled in to view in
entirety. Fixes issue in Chrome, Firefox, and Safari.

h/t @nicknisi for initial fix in #1086

(cherry picked from commit ecfd9a6)

Keyboard.js

@@ -160,7 +160,7 @@ define([
 			}
 			enableNavigation(this.contentNode);
 
-			this._debouncedEnsureRowScroll = miscUtil.debounce(this._ensureRowScroll, this);
+			this._debouncedEnsureScroll = miscUtil.debounce(this._ensureScroll, this);
 		},
 
 		removeRow: function (rowElement) {
@@ -298,6 +298,41 @@ define([
 			}
 		},
 
+		_ensureColumnScroll: function (cellElement) {
+			// summary:
+			//		Ensures that the entire cell is visible in the viewport.
+			//		Called in cases where the grid can scroll horizontally.
+
+			var scrollX = this.getScrollPosition().x;
+			var cellLeft = cellElement.offsetLeft;
+			if (scrollX > cellLeft) {
+				this.scrollTo({ x: cellLeft });
+			}
+			else {
+				var bodyWidth = this.bodyNode.clientWidth;
+				var cellWidth = cellElement.offsetWidth;
+				var cellRight = cellLeft + cellWidth;
+				if (scrollX + bodyWidth < cellRight) {
+					// Adjust so that the right side of the cell and grid body align,
+					// unless the cell is actually wider than the body - then align the left sides
+					this.scrollTo({ x: bodyWidth > cellWidth ? cellRight - bodyWidth : cellLeft });
+				}
+			}
+		},
+
+		_ensureScroll: function (cell, isHeader) {
+			// summary:
+			//		Corrects scroll based on the position of the newly-focused row/cell
+			//		as necessary based on grid configuration and dimensions.
+
+			if(this.cellNavigation && (this.columnSets || this.subRows.length > 1) && !isHeader){
+				this._ensureRowScroll(cell.row.element);
+			}
+			if(this.bodyNode.clientWidth < this.contentNode.offsetWidth){
+				this._ensureColumnScroll(cell.element);
+			}
+		},
+
 		_focusOnNode: function (element, isHeader, event) {
 			var focusedNodeProperty = '_focused' + (isHeader ? 'Header' : '') + 'Node',
 				focusedNode = this[focusedNodeProperty],
@@ -373,9 +408,7 @@ define([
 				on.emit(focusedNode, 'dgrid-cellfocusin', event);
 			}
 
-			if (this.cellNavigation && (this.columnSets || this.subRows.length > 1) && !isHeader) {
-				this._debouncedEnsureRowScroll(cell.row.element);
-			}
+			this._debouncedEnsureScroll(cell, isHeader);
 		},
 
 		focusHeader: function (element) {