Add ability to lock firewall height to basic pane height

New advanced setting: `popupPanelHeightMode`.
Default value: 0

Set to 1 to force the height of the firewall pane
to be no more than the height of the basic pane.

Related feedback:
- https://github.com/uBlockOrigin/uBlock-issues/issues/785#issuecomment-622327450

src/css/popup-fenix.css

@@ -36,9 +36,13 @@ a {
     position: relative;
     }
 #main {
+    align-self: flex-start;
     max-width: 340px;
     min-width: 18em;
     }
+:root.portrait #main {
+    align-self: inherit;
+    }
 hr {
     border: 0;
     border-top: 1px solid #e3e2e3;
@@ -260,6 +264,9 @@ body[data-more=""] #lessButton {
     text-align: right;
     --rule-cell-width: 5em;
     }
+:root.desktop body.vMin #firewall {
+    max-height: 100vh;
+    }
 #firewall > div {
     border: 0;
     direction: ltr;

src/js/background.js

@@ -68,6 +68,7 @@ const µBlock = (( ) => { // jshint ignore:line
         popupFontSize: 'unset',
         popupPanelDisabledSections: 0,
         popupPanelLockedSections: 0,
+        popupPanelHeightMode: 0,
         requestJournalProcessPeriod: 1000,
         selfieAfter: 3,
         strictBlockingBypassDuration: 120,

src/js/messaging.js

@@ -290,6 +290,7 @@ const popupDataFromTabId = function(tabId, tabTitle) {
         popupPanelSections: µbus.popupPanelSections,
         popupPanelDisabledSections: µb.hiddenSettings.popupPanelDisabledSections,
         popupPanelLockedSections: µb.hiddenSettings.popupPanelLockedSections,
+        popupPanelHeightMode: µb.hiddenSettings.popupPanelHeightMode,
         tabId: tabId,
         tabTitle: tabTitle,
         tooltipsDisabled: µbus.tooltipsDisabled

src/js/popup-fenix.js

@@ -639,6 +639,11 @@ let renderOnce = function() {
     if ( popupData.advancedUserEnabled !== true ) {
         uDom('#firewall [title][data-src]').removeAttr('title');
     }
+
+    // This must be done the firewall is populated
+    if ( popupData.popupPanelHeightMode === 1 ) {
+        body.classList.add('vMin');
+    }
 };
 
 /******************************************************************************/