[iOS] Update tab grid page control incognito assets.

This CL updates the page control assets for Incognito with the updated
designs used elsewhere in the app.

Also, this CL removes all of the (unneeded) 1x assets from the tab grid,
removing the associated parts of the Contents.json and BUILD.gn files.

Bug: 1021891
Change-Id: I9f790a89233748e644133676057d900590db8aec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929234
Auto-Submit: Mark Cogan <marq@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719099}

ios/chrome/browser/ui/tab_grid/resources/BUILD.gn

@@ -21,7 +21,6 @@ imageset("new_tab_floating_button") {
 imageset("new_tab_floating_button_incognito") {
   sources = [
     "new_tab_floating_button_incognito.imageset/Contents.json",
-    "new_tab_floating_button_incognito.imageset/new_tab_floating_button_incognito.png",
     "new_tab_floating_button_incognito.imageset/new_tab_floating_button_incognito@2x.png",
     "new_tab_floating_button_incognito.imageset/new_tab_floating_button_incognito@3x.png",
   ]
@@ -38,7 +37,6 @@ imageset("new_tab_toolbar_button") {
 imageset("new_tab_toolbar_button_incognito") {
   sources = [
     "new_tab_toolbar_button_incognito.imageset/Contents.json",
-    "new_tab_toolbar_button_incognito.imageset/new_tab_toolbar_button_incognito.png",
     "new_tab_toolbar_button_incognito.imageset/new_tab_toolbar_button_incognito@2x.png",
     "new_tab_toolbar_button_incognito.imageset/new_tab_toolbar_button_incognito@3x.png",
   ]
@@ -47,7 +45,6 @@ imageset("new_tab_toolbar_button_incognito") {
 imageset("page_control_incognito_tabs") {
   sources = [
     "page_control_incognito_tabs.imageset/Contents.json",
-    "page_control_incognito_tabs.imageset/page_control_incognito_tabs.png",
     "page_control_incognito_tabs.imageset/page_control_incognito_tabs@2x.png",
     "page_control_incognito_tabs.imageset/page_control_incognito_tabs@3x.png",
   ]
@@ -56,7 +53,6 @@ imageset("page_control_incognito_tabs") {
 imageset("page_control_incognito_tabs_selected") {
   sources = [
     "page_control_incognito_tabs_selected.imageset/Contents.json",
-    "page_control_incognito_tabs_selected.imageset/page_control_incognito_tabs_selected.png",
     "page_control_incognito_tabs_selected.imageset/page_control_incognito_tabs_selected@2x.png",
     "page_control_incognito_tabs_selected.imageset/page_control_incognito_tabs_selected@3x.png",
   ]
@@ -65,7 +61,6 @@ imageset("page_control_incognito_tabs_selected") {
 imageset("page_control_regular_tabs") {
   sources = [
     "page_control_regular_tabs.imageset/Contents.json",
-    "page_control_regular_tabs.imageset/page_control_regular_tabs.png",
     "page_control_regular_tabs.imageset/page_control_regular_tabs@2x.png",
     "page_control_regular_tabs.imageset/page_control_regular_tabs@3x.png",
   ]
@@ -74,7 +69,6 @@ imageset("page_control_regular_tabs") {
 imageset("page_control_regular_tabs_selected") {
   sources = [
     "page_control_regular_tabs_selected.imageset/Contents.json",
-    "page_control_regular_tabs_selected.imageset/page_control_regular_tabs_selected.png",
     "page_control_regular_tabs_selected.imageset/page_control_regular_tabs_selected@2x.png",
     "page_control_regular_tabs_selected.imageset/page_control_regular_tabs_selected@3x.png",
   ]
@@ -83,7 +77,6 @@ imageset("page_control_regular_tabs_selected") {
 imageset("page_control_remote_tabs") {
   sources = [
     "page_control_remote_tabs.imageset/Contents.json",
-    "page_control_remote_tabs.imageset/page_control_remote_tabs.png",
     "page_control_remote_tabs.imageset/page_control_remote_tabs@2x.png",
     "page_control_remote_tabs.imageset/page_control_remote_tabs@3x.png",
   ]
@@ -92,7 +85,6 @@ imageset("page_control_remote_tabs") {
 imageset("page_control_remote_tabs_selected") {
   sources = [
     "page_control_remote_tabs_selected.imageset/Contents.json",
-    "page_control_remote_tabs_selected.imageset/page_control_remote_tabs_selected.png",
     "page_control_remote_tabs_selected.imageset/page_control_remote_tabs_selected@2x.png",
     "page_control_remote_tabs_selected.imageset/page_control_remote_tabs_selected@3x.png",
   ]

ios/chrome/browser/ui/tab_grid/resources/new_tab_floating_button_incognito.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "new_tab_floating_button_incognito.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/new_tab_toolbar_button_incognito.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "new_tab_toolbar_button_incognito.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_incognito_tabs.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_incognito_tabs.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_incognito_tabs_selected.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_incognito_tabs_selected.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_regular_tabs.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_regular_tabs.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_regular_tabs_selected.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_regular_tabs_selected.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_remote_tabs.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_remote_tabs.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",

ios/chrome/browser/ui/tab_grid/resources/page_control_remote_tabs_selected.imageset/Contents.json

 {
     "images": [
-        {
-            "idiom": "universal",
-            "scale": "1x",
-            "filename": "page_control_remote_tabs_selected.png"
-        },
         {
             "idiom": "universal",
             "scale": "2x",