Use CSS flexbox in fullscreen mode

file/style/be.bastelstu.wcf.chat.less

@@ -350,6 +350,76 @@
 }
 
 html.fullscreen {
+	#top {
+		height: 0px;
+	}
+	
+	#content {
+		height: 100%;
+	}
+	
+	#timsChatRoomContent {
+		height: 100%;
+		
+		display: -webkit-box;
+		display: -moz-box;
+		display: -ms-flexbox;
+		display: -webkit-flex;
+		display: flex;
+
+		-webkit-box-direction: normal;
+		-moz-box-direction: normal;
+		-webkit-box-orient: vertical;
+		-moz-box-orient: vertical;
+		-webkit-flex-direction: column;
+		-ms-flex-direction: column;
+		flex-direction: column;
+		
+		-webkit-flex-wrap: nowrap;
+		-ms-flex-wrap: nowrap;
+		flex-wrap: nowrap;
+		
+		-webkit-box-pack: start;
+		-moz-box-pack: start;
+		-webkit-justify-content: flex-start;
+		-ms-flex-pack: start;
+		justify-content: flex-start;
+		
+		-webkit-align-content: stretch;
+		-ms-flex-line-pack: stretch;
+		align-content: stretch;
+		-webkit-box-align: stretch;
+		-moz-box-align: stretch;
+		-webkit-align-items: stretch;
+		-ms-flex-align: stretch;
+		align-items: stretch;
+		
+		> fieldset {
+			-webkit-box-ordinal-group: 1;
+			-moz-box-ordinal-group: 1;
+			-webkit-order: 0;
+			-ms-flex-order: 0;
+			order: 0;
+			-webkit-box-flex: 1;
+			-moz-box-flex: 1;
+			-webkit-flex: 1 100 auto;
+			-ms-flex: 1 100 auto;
+			flex: 1 100 auto;
+			-webkit-align-self: auto;
+			-ms-flex-item-align: auto;
+			align-self: auto;
+			
+			> div {
+				height: 100%;
+			}
+		}
+		
+		#timsChatControls {
+			margin-bottom: 15px;
+		}
+	}
+
+	
 	height: 100%;
 	overflow: hidden;