`display: block` technique for rendering diacritics

diacritics.patch

diff --git a/src/commands/math/commands.js b/src/commands/math/commands.js
index f763480..a9479f7 100644
--- a/src/commands/math/commands.js
+++ b/src/commands/math/commands.js
@@ -495,7 +495,7 @@ var DiacriticAbove = P(MathCommand, function(_, super_) {
     var htmlTemplate =
         '<span class="mq-diacritic mq-non-leaf">'
       +   '<span class="mq-diacritic-above">'+symbol+'&nbsp;</span>'
-      +   '<span class="mq-non-leaf mq-inset">&0</span>'
+      +   '<span class="mq-diacritic-stem mq-inset">&0</span>'
       + '</span>'
     ;
 
@@ -507,8 +507,8 @@ var DiacriticAbove = P(MathCommand, function(_, super_) {
       if (!(cmd.ctrlSeq in LOW_LETTERS)) allLow = false;
       if (cmd.ctrlSeq === 't') anyTs = true;
     });
-    this.jQ.toggleClass('mq-diacritic-low', allLow)
-           .toggleClass('mq-diacritic-t', anyTs);
+    block.jQ.prev().toggleClass('mq-diacritic-low', allLow)
+                   .toggleClass('mq-diacritic-t', anyTs);
   };
   var LOW_ROMAN_LETTERS = 'acegmnopqrstuvwxyz';
   var LOW_GREEK_LETTERS = 'alpha gamma eta iota kappa mu nu rho sigma tau chi omega varphi epsilon varepsilon pi varpi varsigma upsilon digamma varkappa varrho psi'.split(' ');
diff --git a/src/css/math.less b/src/css/math.less
index 9d4658b..597aeab 100644
--- a/src/css/math.less
+++ b/src/css/math.less
@@ -295,29 +295,25 @@
     padding-top: 1px;
   }
 
-  .mq-diacritic {
-    position: relative;
-
-    padding-top: .2em;
+  .mq-diacritic-above {
+    display: block;
+    text-align: center;
+    height: 0;
+    // use transparent border not margin or padding as Chrome workaround:
+    // https://bugs.chromium.org/p/chromium/issues/detail?id=617763#c3
+    border-top: .15em solid transparent;
+    border-bottom: .15em solid transparent;
     &.mq-diacritic-low {
-      padding-top: 0;
+      border-bottom: 0;
+      margin-bottom: -.05em;
+      margin-left: -.2em;
       &.mq-diacritic-t {
-        padding: .1em;
+        margin-bottom: 0;
       }
     }
   }
-  .mq-diacritic-above {
-    position: absolute;
-    left: 0;
-    right: 0;
-    text-align: center;
-
-    top: .06em; // yes, really, .05em isn't low enough in Chrome,
-                             // .07em is too low in Firefox & Safari
-  }
-  .mq-diacritic-low > .mq-diacritic-above {
-    left: -.1em;
-    right: .1em;
+  .mq-diacritic-stem {
+    display: block;
   }
 
   .mq-large-operator {