WebUI Polymer 2: Don't include dir-mixin.html in the final bundle.

Locally modify Polymer 2 to exclude dir-mixin.html, since it is unnecessary
currently (we don't directly* use any :dir() CSS rules), and also causes a
performance regression (more notice-able in chrome://md-user-manager), due to a
Regex running over a fairly large amount of text (because of inlined PNG background
images).

*The only usage of :dir() was in paper-input-container.html, which is still used
by ChromeOS <gaia-input> element. Modified <paper-input-container> to directly
use :host-context instead. Also :dir() is not implemented in Chrome, so we should
not be using it in our own code anyway.

Ideally the usage of this mixin should be exposed as a Polymer option, so that
we don't need to manually modify our local Polymer 2 copy.

Bug: 899603
Change-Id: Ia20535fb2adb2c9a6bebf3046e4405a4ca31af6c
Reviewed-on: https://chromium-review.googlesource.com/c/1306515Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604759}

third_party/polymer/README.chromium

@@ -44,6 +44,9 @@ the Crisper tool (https://github.com/PolymerLabs/crisper).
   handler code which was hiding ripples for pointer interactions.
 - Bundled and minified Polymer 2 with minify_polymer.py, since Polymer 2 repo
   does not distribute minified files (unlike Polymer 1).
+- Note that the Polymer 2 bundle does not include dir-mixin.html which is
+  responsible for polyfylling :dir() CSS rules, because it causes a performance
+  regression (and it is unnecessary), see crbug.com/899603 for more context.
 
 To restore a content of the 'components-chromium' directory from scratch, run
 ./v1_0/reproduce.sh on a Linux machine.

third_party/polymer/v1_0/chromium.patch

@@ -144,3 +144,41 @@ index 2e63d3731be1..217c7ff1414c 100644
      });
  
      /**
+diff --git a/components-chromium/paper-input/paper-input-container.html b/components-chromium/paper-input/paper-input-container.html
+index 55714942c93c..46fb9adf6a04 100644
+--- a/components-chromium/paper-input/paper-input-container.html
++++ b/components-chromium/paper-input/paper-input-container.html
+@@ -254,8 +254,8 @@ This element is `display:block` by default, but you can set the `inline` attribu
+         @apply --paper-input-container-label-floating;
+       }
+ 
+-      :host(:dir(rtl)) .input-content.label-is-floating ::slotted(label),
+-      :host(:dir(rtl)) .input-content.label-is-floating ::slotted(.paper-input-label) {
++      :host-context([dir="rtl"]) .input-content.label-is-floating ::slotted(label),
++      :host-context([dir="rtl"]) .input-content.label-is-floating ::slotted(.paper-input-label) {
+         right: 0;
+         left: auto;
+         transform-origin: right top;
+diff --git a/components-chromium/polymer2/lib/legacy/legacy-element-mixin.html b/components-chromium/polymer2/lib/legacy/legacy-element-mixin.html
+index 7306c651407e..9c88699a3924 100644
+--- a/components-chromium/polymer2/lib/legacy/legacy-element-mixin.html
++++ b/components-chromium/polymer2/lib/legacy/legacy-element-mixin.html
+@@ -11,7 +11,6 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
+ <link rel="import" href="../../../shadycss/apply-shim.html">
+ <link rel="import" href="../mixins/element-mixin.html">
+ <link rel="import" href="../mixins/gesture-event-listeners.html">
+-<link rel="import" href="../mixins/dir-mixin.html">
+ <link rel="import" href="../utils/mixin.html">
+ <link rel="import" href="../utils/import-href.html">
+ <link rel="import" href="../utils/render-status.html">
+@@ -47,9 +46,8 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
+      * @extends {base}
+      * @implements {Polymer_ElementMixin}
+      * @implements {Polymer_GestureEventListeners}
+-     * @implements {Polymer_DirMixin}
+      */
+-    const legacyElementBase = Polymer.DirMixin(Polymer.GestureEventListeners(Polymer.ElementMixin(base)));
++    const legacyElementBase = Polymer.GestureEventListeners(Polymer.ElementMixin(base));
+ 
+     /**
+      * Map of simple names to touch action names

third_party/polymer/v1_0/components-chromium/paper-input/paper-input-container.html

@@ -254,8 +254,8 @@ This element is `display:block` by default, but you can set the `inline` attribu
         @apply --paper-input-container-label-floating;
       }
 
-      :host(:dir(rtl)) .input-content.label-is-floating ::slotted(label),
-      :host(:dir(rtl)) .input-content.label-is-floating ::slotted(.paper-input-label) {
+      :host-context([dir="rtl"]) .input-content.label-is-floating ::slotted(label),
+      :host-context([dir="rtl"]) .input-content.label-is-floating ::slotted(.paper-input-label) {
         right: 0;
         left: auto;
         transform-origin: right top;

third_party/polymer/v1_0/reproduce.sh

@@ -68,9 +68,6 @@ sed -i 's/['"$NBSP"']/\\u00A0/g' components/polymer/polymer-mini.html
 rsync -c --delete -r -v --exclude-from="rsync_exclude.txt" \
     --prune-empty-dirs "components/" "components-chromium/"
 
-echo 'Minifying Polymer 2, since it comes non-minified from bower.'
-python minify_polymer.py
-
 find "components-chromium/" -name "*.html" \
   ! -path "components-chromium/polymer2*" | \
   xargs grep -l "<script>" | \
@@ -85,6 +82,9 @@ done
 # a Polymer issue and/or pull request to minimize these patches.
 patch -p1 --forward -r - < chromium.patch
 
+echo 'Minifying Polymer 2, since it comes non-minified from bower.'
+python minify_polymer.py
+
 # Undo any changes in paper-ripple, since Chromium's implementation is a fork of
 # the original paper-ripple.
 git checkout -- components-chromium/paper-ripple/*