Adds CupsProxyService chrome flag

DDoc: go/cups-plugin

Adds flag to condition above printing pipeline on. Will be used to
condition the CupsProxyService startup.

Bug: chromium:495409
Test: build unit_tests & run CheckHistograms + EveryFlagHasMetadata
Change-Id: Id4b75ceca33a9930992e1732537621cbc154a64b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1601835Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Commit-Queue: Luum Habtemariam <luum@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658334}

chrome/browser/about_flags.cc

@@ -3197,6 +3197,9 @@ const FeatureEntry kFeatureEntries[] = {
     {"enable-arc-cups-api", flag_descriptions::kArcCupsApiName,
      flag_descriptions::kArcCupsApiDescription, kOsCrOS,
      FEATURE_VALUE_TYPE(features::kArcCupsApi)},
+    {"enable-cros-vm-cups-proxy", flag_descriptions::kCrosVmCupsProxyName,
+     flag_descriptions::kCrosVmCupsProxyDescription, kOsCrOS,
+     FEATURE_VALUE_TYPE(features::kCrosVmCupsProxy)},
 #endif  // OS_CHROMEOS
 
 #if defined(OS_CHROMEOS)

chrome/browser/flag-metadata.json

@@ -937,6 +937,11 @@
     "owners": [ "essential-inputs-team@google.com" ],
     "expiry_milestone": 76
   },
+  {
+    "name": "enable-cros-vm-cups-proxy",
+    "owners": [ "//chrome/services/cups_proxy/OWNERS" ],
+    "expiry_milestone": 78
+  },
   {
     "name": "enable-custom-context-menu",
     "owners": [ "chrome-android-app" ],

chrome/browser/flag_descriptions.cc

@@ -2969,6 +2969,10 @@ const char kCrostiniUsbSupportName[] = "Crostini Usb Support";
 const char kCrostiniUsbSupportDescription[] =
     "Enable mounting Usb devices in Crostini.";
 
+const char kCrosVmCupsProxyName[] = "Chrome OS CUPS Proxy";
+const char kCrosVmCupsProxyDescription[] =
+    "Supports printing from VMs on Chrome OS.";
+
 const char kCryptAuthV2EnrollmentName[] = "CryptAuth v2 Enrollment";
 const char kCryptAuthV2EnrollmentDescription[] =
     "Use the CryptAuth v2 Enrollment protocol.";

chrome/browser/flag_descriptions.h

@@ -1789,6 +1789,9 @@ extern const char kCrostiniUsbAllowUnsupportedDescription[];
 extern const char kCrostiniUsbSupportName[];
 extern const char kCrostiniUsbSupportDescription[];
 
+extern const char kCrosVmCupsProxyName[];
+extern const char kCrosVmCupsProxyDescription[];
+
 extern const char kCryptAuthV2EnrollmentName[];
 extern const char kCryptAuthV2EnrollmentDescription[];
 

chrome/common/chrome_features.cc

@@ -707,6 +707,10 @@ const base::Feature kUseSameCacheForMedia{"UseSameCacheForMedia",
 const base::Feature kArcCupsApi{"ArcCupsApi",
                                 base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables or disables serving printing requests from VMs on ChromeOS.
+const base::Feature kCrosVmCupsProxy{"CrosVmCupsProxy",
+                                     base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables or disables pin quick unlock.
 // TODO(https://crbug.com/935613): Remove this & the backing code.
 const base::Feature kQuickUnlockPin{"QuickUnlockPin",

chrome/common/chrome_features.h

@@ -444,6 +444,8 @@ extern const base::Feature kUseSameCacheForMedia;
 #if defined(OS_CHROMEOS)
 COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kArcCupsApi;
 
+COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kCrosVmCupsProxy;
+
 COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kQuickUnlockPin;
 
 COMPONENT_EXPORT(CHROME_FEATURES)

tools/metrics/histograms/enums.xml

@@ -33829,6 +33829,7 @@ from previous Chrome versions.
       label="CrossOriginMediaPlaybackRequiresUserGesture:disabled"/>
   <int value="-296179618" label="CookiesWithoutSameSiteMustBeSecure:enabled"/>
   <int value="-290672626" label="enable-asm-wasm"/>
+  <int value="-290329565" label="CrosVmCupsProxy:disabled"/>
   <int value="-288316828" label="enable-delegated-renderer"/>
   <int value="-286603268" label="hide-android-files-in-files-app"/>
   <int value="-284547865" label="UnifiedConsent:enabled"/>
@@ -34131,6 +34132,7 @@ from previous Chrome versions.
   <int value="173288154" label="PrintPdfAsImage:enabled"/>
   <int value="178337215" label="enable-md-history"/>
   <int value="180074362" label="memory-pressure-thresholds"/>
+  <int value="181150000" label="CrosVmCupsProxy:enabled"/>
   <int value="183208826" label="TabGroups:enabled"/>
   <int value="185991204" label="enable-webrtc-srtp-encrypted-headers"/>
   <int value="188610022" label="NewMessageListView:enabled"/>