Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/paper-progress/README.md

-paper-progress
-===================
-
-The progress bars are for situations where the percentage completed can be
-determined. They give users a quick sense of how much longer an operation
-will take.
-
-Example:
-
-```html
-<paper-progress value="10"></paper-progress>
-```
-
-There is also a secondary progress which is useful for displaying intermediate
-progress, such as the buffer level during a streaming playback progress bar.
-
-Example:
-
-```html
-<paper-progress value="10" secondary-progress="30"></paper-progress>
-```
-
-### Styling progress bar:
-
-To change the active progress bar color:
-
-```css
-paper-progress {
-  --paper-progress-active-color: #e91e63;
-}
-```
-
-To change the secondary progress bar color:
-
-```css
-paper-progress {
-  --paper-progress-secondary-color: #f8bbd0;
-}
-```
-
-To change the progress bar background color:
-
-```css
-paper-progress {
-  --paper-progress-container-color: #64ffda;
-}
-```
-
-Add the class `transiting` to a `<paper-progress>` to animate the progress bar when
-the value changed. You can also customize the transition:
-
-```css
-paper-progress {
-  --paper-progress-transition-duration: 0.08s;
-  --paper-progress-transition-timing-function: ease;
-  --paper-progress-transition-transition-delay: 0s;
-}
-```