Please update the commit message based on the new diff

[skip ci]

Three commits that has been squashed:

Anchor loader pulsar to avoid jumping around

 * Hide iframe until load message is received.

 * Use absolute positioning for loader.

Fix iframe hiding to avoid breaking stl, pdb, and images

 * Switch to using `opacity: 0.0` instead of `display: none` to hide
   iframes that are still being built.  Use of `display: none` was
   causing OpenGL-based renderers (pdb and 3D-object) to fail, and was
   disabling image zoom for large images.

Only style the mfr loader'

Author: NyanHelsing

mfr/server/static/css/mfr.css

@@ -3,23 +3,23 @@
 This CSS was stripped out of base.css from the osf-style repo.
 */
 
-.ball-pulse > div:nth-child(0) {
+#mfrIframe .ball-pulse > div:nth-child(0) {
   -webkit-animation: scale 0.75s -0.36s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
           animation: scale 0.75s -0.36s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
 }
-.ball-pulse > div:nth-child(1) {
+#mfrIframe .ball-pulse > div:nth-child(1) {
   -webkit-animation: scale 0.75s -0.24s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
           animation: scale 0.75s -0.24s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
 }
-.ball-pulse > div:nth-child(2) {
+#mfrIframe .ball-pulse > div:nth-child(2) {
   -webkit-animation: scale 0.75s -0.12s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
           animation: scale 0.75s -0.12s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
 }
-.ball-pulse > div:nth-child(3) {
+#mfrIframe .ball-pulse > div:nth-child(3) {
   -webkit-animation: scale 0.75s 0s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
           animation: scale 0.75s 0s infinite cubic-bezier(0.2, 0.68, 0.18, 1.08);
 }
-.ball-pulse > div {
+#mfrIframe .ball-pulse > div {
   background-color: #fff;
   width: 15px;
   height: 15px;
@@ -31,10 +31,29 @@ This CSS was stripped out of base.css from the osf-style repo.
 }
 
 
-.ball-dark > div {
+#mfrIframe .ball-dark > div {
   background-color: #337AB7;
 }
 
-.embed-responsive-pdf {
+#mfrIframe .ball-scale {
+    position: absolute;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    width: 100%;
+    height: 250px;
+    top: 0;
+    left: 0;
+}
+
+#mfrIframe .embed-responsive-pdf {
     padding-bottom: 95%;
 }
+
+#mfrIframe iframe {
+    opacity: 0.0;
+}
+
+#mfrIframe {
+    min-height: 250px;
+}

mfr/server/static/js/mfr.child.js

@@ -17,7 +17,7 @@
                 }
             });
         });
-    });
+    }, false);
 
     window.addEventListener('resize', function () {
         window.pymChild.sendHeight();

mfr/server/static/js/mfr.js

@@ -80,9 +80,10 @@
             self.pymParent.iframe.setAttribute('sandbox', 'allow-scripts allow-popups allow-same-origin');
 
             self.pymParent.el.appendChild(self.spinner);
-            $(self.pymParent.iframe).on('load', function () {
+            $(self.pymParent.iframe).on('load', function() {
                 self.pymParent.el.removeChild(self.spinner);
-            });
+                this.style.opacity = "1.0"
+            })
 
             self.pymParent.onMessage('embed', function(message) {
                 _addClass(self.pymParent.el, 'embed-responsive');