Added subtle background for collapsed icons

src/vs/editor/contrib/folding/browser/arrow-collapse-dark.svg

@@ -3,20 +3,22 @@
 <svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
 	 viewBox="0 0 15 15" style="enable-background:new 0 0 15 15;" xml:space="preserve">
 <style type="text/css">
-	.st0{fill:#5A5A5A;}
-	.st1{fill:none;stroke:#C5C5C5;stroke-miterlimit:10;}
+	.st0{opacity:9.000000e-002;fill:#FFFFFF;}
+	.st1{fill:#5A5A5A;}
+	.st2{fill:none;stroke:#C5C5C5;stroke-miterlimit:10;}
 </style>
+<rect x="2" y="2" class="st0" width="11" height="11"/>
 <g id="iconBg">
 	<g>
-		<path class="st0" d="M12,3v9H3V3H12 M13,2H2v11h11V2L13,2z"/>
+		<path class="st1" d="M12,3v9H3V3H12 M13,2H2v11h11V2L13,2z"/>
 	</g>
 </g>
 <g>
 	<g>
-		<line class="st1" x1="11" y1="7.5" x2="4" y2="7.5"/>
+		<line class="st2" x1="11" y1="7.5" x2="4" y2="7.5"/>
 	</g>
 	<g>
-		<line class="st1" x1="7.5" y1="4" x2="7.5" y2="11"/>
+		<line class="st2" x1="7.5" y1="4" x2="7.5" y2="11"/>
 	</g>
 </g>
 </svg>

src/vs/editor/contrib/folding/browser/arrow-collapse.svg

@@ -3,16 +3,18 @@
 <svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
 	 viewBox="0 0 15 15" style="enable-background:new 0 0 15 15;" xml:space="preserve">
 <style type="text/css">
-	.st0{fill:none;stroke:#6B6B6B;stroke-miterlimit:10;}
-	.st1{fill:#B6B6B6;}
+	.st0{fill:#E8E8E8;}
+	.st1{fill:none;stroke:#6B6B6B;stroke-miterlimit:10;}
+	.st2{fill:#B6B6B6;}
 </style>
+<rect x="2" y="2" class="st0" width="11" height="11"/>
 <g>
-	<line class="st0" x1="7.5" y1="4" x2="7.5" y2="11"/>
-	<line class="st0" x1="11" y1="7.5" x2="4" y2="7.5"/>
+	<line class="st1" x1="7.5" y1="4" x2="7.5" y2="11"/>
+	<line class="st1" x1="11" y1="7.5" x2="4" y2="7.5"/>
 </g>
 <g id="iconBg">
 	<g>
-		<path class="st1" d="M12,3v9H3V3H12 M13,2H2v11h11V2L13,2z"/>
+		<path class="st2" d="M12,3v9H3V3H12 M13,2H2v11h11V2L13,2z"/>
 	</g>
 </g>
 </svg>