Replace most remaining Element.setAttribute("style", ...) usage with Element.style = ... instead

This should hopefully be useful in environments where restrictive CSPs are in effect.
In most cases the replacement is entirely straighforward, and there's only a couple of special cases:
 - For the `src/display/font_loader.js` and `web/pdf_outline_viewer.js `cases, since the elements aren't appended to the document yet, it shouldn't matter if the style properties are set one-by-one rather than all at once.
 - For the `web/debugger.js` case, there's really no need to set the `padding` inline at all and the definition was simply moved to `web/viewer.css` instead.

*Please note:* There's still *a single* case left, in `web/toolbar.js` for setting the width of the zoom dropdown, which is left intact for now.
The reasons are that this particular case shouldn't matter for users of the general PDF.js library, and that it'd make a lot more sense to just try and re-factor that very old code anyway (thus fixing the `setAttribute` usage in the process).

web/debugger.js

@@ -67,7 +67,6 @@ var FontInspector = (function FontInspectorClosure() {
     manager: null,
     init: function init(pdfjsLib) {
       var panel = this.panel;
-      panel.setAttribute("style", "padding: 5px;");
       var tmp = document.createElement("button");
       tmp.addEventListener("click", resetSelection);
       tmp.textContent = "Refresh";
@@ -178,7 +177,6 @@ var StepperManager = (function StepperManagerClosure() {
     manager: null,
     init: function init(pdfjsLib) {
       var self = this;
-      this.panel.setAttribute("style", "padding: 5px;");
       stepperControls = document.createElement("div");
       stepperChooser = document.createElement("select");
       stepperChooser.addEventListener("change", function(event) {
@@ -468,9 +466,7 @@ var Stats = (function Stats() {
     name: "Stats",
     panel: null,
     manager: null,
-    init(pdfjsLib) {
-      this.panel.setAttribute("style", "padding: 5px;");
-    },
+    init(pdfjsLib) {},
     enabled: false,
     active: false,
     // Stats specific functions.

web/pdf_outline_viewer.js

@@ -94,16 +94,11 @@ class PDFOutlineViewer {
    * @private
    */
   _setStyles(element, { bold, italic }) {
-    let styleStr = "";
     if (bold) {
-      styleStr += "font-weight: bold;";
+      element.style.fontWeight = "bold";
     }
     if (italic) {
-      styleStr += "font-style: italic;";
-    }
-
-    if (styleStr) {
-      element.setAttribute("style", styleStr);
+      element.style.fontStyle = "italic";
     }
   }
 

web/secondary_toolbar.js

@@ -340,10 +340,8 @@ class SecondaryToolbar {
     if (this.containerHeight === this.previousContainerHeight) {
       return;
     }
-    this.toolbarButtonContainer.setAttribute(
-      "style",
-      "max-height: " + (this.containerHeight - SCROLLBAR_PADDING) + "px;"
-    );
+    this.toolbarButtonContainer.style.maxHeight = `${this.containerHeight -
+      SCROLLBAR_PADDING}px`;
 
     this.previousContainerHeight = this.containerHeight;
   }

web/ui_utils.js

@@ -890,10 +890,7 @@ class ProgressBar {
     const container = viewer.parentNode;
     const scrollbarWidth = container.offsetWidth - viewer.offsetWidth;
     if (scrollbarWidth > 0) {
-      this.bar.setAttribute(
-        "style",
-        "width: calc(100% - " + scrollbarWidth + "px);"
-      );
+      this.bar.style.width = `calc(100% - ${scrollbarWidth}px)`;
     }
   }
 

web/viewer.css

@@ -1483,6 +1483,9 @@ html[dir='rtl'] #documentPropertiesOverlay .row > * {
   right: 0;
   top: 27px;
 }
+#PDFBug .panels > div {
+  padding: 5px;
+}
 #PDFBug button.active {
   font-weight: bold;
 }