Reland "Add about:flag for feature PdfIsolation""

This reverts commit abc55490.
This cl had to be reverted to allow the revert of its predecessor.
Now that the predecessor is relanded, it can be re-applied.

Original CL at https://chromium-review.googlesource.com/c/chromium/src/+/956488

TBR=jam@chromium.org

Bug: 809614
Change-Id: I7a4eceed9d8a7df5e7a60ae79b226eab8a0dd9ad
Reviewed-on: https://chromium-review.googlesource.com/961105Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542879}

chrome/browser/about_flags.cc

@@ -3736,6 +3736,10 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kVizHitTestDrawQuadDescription, kOsAll,
      FEATURE_VALUE_TYPE(features::kEnableVizHitTestDrawQuad)},
 
+    {"pdf-isolation", flag_descriptions::kPdfIsolationName,
+     flag_descriptions::kPdfIsolationDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(features::kPdfIsolation)},
+
     // NOTE: Adding a new flag requires adding a corresponding entry to enum
     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
     // Histograms" in tools/metrics/histograms/README.md (run the

chrome/browser/flag_descriptions.cc

@@ -1161,6 +1161,10 @@ const char kPasswordSearchMobileName[] = "Password search";
 const char kPasswordSearchMobileDescription[] =
     "Search functionality in password settings.";
 
+const char kPdfIsolationName[] = "PDF Isolation";
+const char kPdfIsolationDescription[] =
+    "Render PDF files from different origins in different plugin processes.";
+
 const char kPermissionsBlacklistName[] = "Permissions Blacklist";
 const char kPermissionsBlacklistDescription[] =
     "Enables the Permissions Blacklist, which blocks permissions for "

chrome/browser/flag_descriptions.h

@@ -724,6 +724,9 @@ extern const char kPasswordImportDescription[];
 extern const char kPasswordSearchMobileName[];
 extern const char kPasswordSearchMobileDescription[];
 
+extern const char kPdfIsolationName[];
+extern const char kPdfIsolationDescription[];
+
 extern const char kPermissionsBlacklistName[];
 extern const char kPermissionsBlacklistDescription[];
 

tools/metrics/histograms/enums.xml

@@ -26014,6 +26014,7 @@ from previous Chrome versions.
   <int value="-1235586511" label="enable-datasaver-prompt"/>
   <int value="-1225198073" label="ReaderModeInCCT:disabled"/>
   <int value="-1224962996" label="PwaImprovedSplashScreen:disabled"/>
+  <int value="-1222805155" label="PdfIsolation:enabled"/>
   <int value="-1218608640" label="disable-offline-load-stale-cache"/>
   <int value="-1217425153" label="ChromeHomeClearUrlOnOpen:enabled"/>
   <int value="-1216837777" label="clear-data-reduction-proxy-data-savings"/>
@@ -26096,6 +26097,7 @@ from previous Chrome versions.
   <int value="-1039555838" label="GamepadExtensions:enabled"/>
   <int value="-1034344165" label="V8NoTurbo:disabled"/>
   <int value="-1033738911" label="enable-mac-views-dialogs"/>
+  <int value="-1031350684" label="PdfIsolation:disabled"/>
   <int value="-1029920490" label="IdleTimeSpellChecking:enabled"/>
   <int value="-1028733699" label="MacViewsWebUIDialogs:disabled"/>
   <int value="-1027254093" label="LockScreenNotifications:disabled"/>