[NTP] Create icons/ subdirectory

More icons are coming for new NTP features. Add a subdirectory for
them and move existing icons.

Bug: None
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I3424d626d01fad8383f4d04e733510563c3e959d
Reviewed-on: https://chromium-review.googlesource.com/1137031
Commit-Queue: Mathieu Perreault <mathp@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575288}

chrome/browser/resources/local_ntp/custom_backgrounds.css

@@ -107,20 +107,20 @@ html[dir=rtl] .bg-option-img {
 }
 
 #edit-bg-google-photos .bg-option-img {
-  background: url(photos.svg) no-repeat center;
+  background: url(icons/photos.svg) no-repeat center;
 }
 
 #edit-bg-default-wallpapers .bg-option-img {
-  background: url(wallpapers.svg) no-repeat center;
+  background: url(icons/wallpapers.svg) no-repeat center;
 }
 
 #edit-bg-upload-image .bg-option-img {
-  background: rgb(241, 243, 244) url(upload.svg) no-repeat center;
+  background: rgb(241, 243, 244) url(icons/upload.svg) no-repeat center;
   border-radius: 50%;
 }
 
 #edit-bg-restore-default .bg-option-img {
-  background: rgb(241, 243, 244) url(chrome.svg)  no-repeat center;
+  background: rgb(241, 243, 244) url(icons/chrome.svg)  no-repeat center;
   border-radius: 50%;
 }
 

chrome/browser/resources/local_ntp/local_ntp.css

@@ -410,7 +410,7 @@ html[dir=rtl] .md #fakebox-cursor {
 }
 
 #fakebox-microphone {
-  background: url(googlemic_clr_24px.svg) no-repeat center;
+  background: url(icons/googlemic_clr_24px.svg) no-repeat center;
   background-size: 24px 24px;
   bottom: 0;
   cursor: pointer;