Use Lato as the sans-serif font for v2.

services/web/public/stylesheets/app/editor/toolbar.less

@@ -143,7 +143,7 @@
 .toolbar-label {
 	display: none;
 	margin: 0 4px;
-	font-size: 12px;
+	font-size: @toolbar-font-size;
 	font-weight: 600;
 	margin-bottom: 2px;
 	vertical-align: middle;

services/web/public/stylesheets/core/_common-variables.less

@@ -20,14 +20,9 @@
 //== Typography
 //
 //## Font, line-height, and color for body text, headings, and more.
-
-@import url(https://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700);
-//@import url(https://fonts.googleapis.com/css?family=PT+Serif:400,600,700);
-//@import url(https://fonts.googleapis.com/css?family=PT+Serif:400,400i,700,700i);
-@import url(https://fonts.googleapis.com/css?family=Merriweather:400,400i,700,700i);
-
 @font-family-sans-serif:  "Open Sans", sans-serif;
 @font-family-serif:       "Merriweather", serif;
+
 //** Default monospace fonts for `<code>`, `<kbd>`, and `<pre>`.
 @font-family-monospace:   Menlo, Monaco, Consolas, "Courier New", monospace;
 @font-family-base:        @font-family-sans-serif;
@@ -898,6 +893,7 @@
 @toolbar-btn-active-color       : white;
 @toolbar-btn-active-bg-color    : @link-color;
 @toolbar-btn-active-shadow      : inset 0 3px 5px rgba(0, 0, 0, 0.225);
+@toolbar-font-size              : 12px;
 @toolbar-alt-bg-color           : #fafafa;
 @toolbar-icon-btn-color         : @gray-light;
 @toolbar-icon-btn-hover-color   : @gray-dark;

services/web/public/stylesheets/core/ol-variables.less

@@ -1,6 +1,9 @@
 @import "./_common-variables.less";
 
 @is-overleaf: true;
+
+@font-family-sans-serif: "Lato", sans-serif;
+
 @header-height: 68px;
 @footer-height: 50px;
 
@@ -176,6 +179,8 @@
 @toolbar-icon-btn-hover-shadow    : none;
 @toolbar-border-bottom            : 1px solid @toolbar-border-color;
 @toolbar-icon-btn-hover-boxshadow : none;
+@toolbar-font-size                : 13px;
+
 // Editor file-tree
 @file-tree-bg                     : @ol-blue-gray-4;
 @file-tree-line-height            : 2.05;

services/web/public/stylesheets/ol-style.less

@@ -1,3 +1,6 @@
+@import url(https://fonts.googleapis.com/css?family=Lato:300,400,700&subset=latin-ext);
+@import url(https://fonts.googleapis.com/css?family=Merriweather:400,400i,700,700i);
+
 // Core variables and mixins
 @import "core/ol-variables.less";
 @import "app/ol-style-guide.less";

services/web/public/stylesheets/style.less

@@ -1,3 +1,6 @@
+@import url(https://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700);
+@import url(https://fonts.googleapis.com/css?family=Merriweather:400,400i,700,700i);
+
 // Core variables and mixins
 @import "core/variables.less";
 @import "_style_includes.less";