Use Opaque Canvas where possible

src/display/api.js

@@ -688,7 +688,7 @@ var WorkerTransport = (function WorkerTransportClosure() {
         info('The worker has been disabled.');
       }
     }
-//#endif    
+//#endif
     // Either workers are disabled, not supported or have thrown an exception.
     // Thus, we fallback to a faked worker.
     globalScope.PDFJS.disableWorker = true;

web/page_view.js

@@ -462,7 +462,7 @@ var PageView = function pageView(container, id, scale,
     this.canvas = canvas;
 
     var scale = this.scale;
-    var ctx = canvas.getContext('2d');
+    var ctx = canvas.getContext('2d', {alpha: false});
     var outputScale = getOutputScale(ctx);
 
     if (USE_ONLY_CSS_ZOOM) {

web/text_layer_builder.js

@@ -53,7 +53,7 @@ var TextLayerBuilder = function textLayerBuilder(options) {
   this.renderLayer = function textLayerBuilderRenderLayer() {
     var textDivs = this.textDivs;
     var canvas = document.createElement('canvas');
-    var ctx = canvas.getContext('2d');
+    var ctx = canvas.getContext('2d', {alpha: false});
 
     // No point in rendering so many divs as it'd make the browser unusable
     // even after the divs are rendered

web/thumbnail_view.js

@@ -111,7 +111,7 @@ var ThumbnailView = function thumbnailView(container, id, defaultViewport) {
 
     ring.appendChild(canvas);
 
-    var ctx = canvas.getContext('2d');
+    var ctx = canvas.getContext('2d', {alpha: false});
     ctx.save();
     ctx.fillStyle = 'rgb(255, 255, 255)';
     ctx.fillRect(0, 0, this.canvasWidth, this.canvasHeight);