Add field trial param and about:flag for IsolatedPrerender NSP

Leaves the command line flag for use in browsertesting and in the
about:flag.

Note: The browser tests can't set features with params because of this:
http://shortn/_ZytN1SHiqN

Bug: 1082505
Change-Id: I474fe012c6a00b15f38d70334d677a29815b24b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2265178Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782107}

chrome/browser/about_flags.cc

@@ -42,6 +42,7 @@
 #include "chrome/browser/permissions/quiet_notification_permission_ui_config.h"
 #include "chrome/browser/predictors/loading_predictor_config.h"
 #include "chrome/browser/prerender/isolated/isolated_prerender_features.h"
+#include "chrome/browser/prerender/isolated/isolated_prerender_params.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
 #include "chrome/browser/resource_coordinator/tab_manager_features.h"
 #include "chrome/browser/search/ntp_features.h"
@@ -2714,6 +2715,10 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_WITH_PARAMS_VALUE_TYPE(features::kIsolatePrerenders,
                                     kIsolatedPrerenderFeatureWithPrefetchLimit,
                                     "Prefetch Limit")},
+    {"enable-google-srp-isolated-prerender-nsp",
+     flag_descriptions::kEnableSRPIsolatedPrerendersNSPName,
+     flag_descriptions::kEnableSRPIsolatedPrerendersNSPDescription, kOsAll,
+     SINGLE_VALUE_TYPE(kIsolatedPrerenderEnableNSPCmdLineFlag)},
     {"allow-insecure-localhost", flag_descriptions::kAllowInsecureLocalhostName,
      flag_descriptions::kAllowInsecureLocalhostDescription, kOsAll,
      SINGLE_VALUE_TYPE(switches::kAllowInsecureLocalhost)},

chrome/browser/flag-metadata.json

@@ -1661,6 +1661,11 @@
     "owners": [ "reillyg@chromium.org", "raphael.kubo.da.costa@intel.com" ],
     "expiry_milestone": 86
   },
+  {
+    "name": "enable-google-srp-isolated-prerender-nsp",
+    "owners": [ "//chrome/browser/prerender/OWNERS" ],
+    "expiry_milestone": 90
+  },
   {
     "name": "enable-google-srp-isolated-prerender-probing",
     "owners": [ "//chrome/browser/prerender/OWNERS" ],

chrome/browser/flag_descriptions.cc

@@ -740,6 +740,11 @@ const char kEnableSRPIsolatedPrerenderProbingName[] =
 const char kEnableSRPIsolatedPrerenderProbingDescription[] =
     "Enable probing checks for Isolated Prerenders which will block commit.";
 
+const char kEnableSRPIsolatedPrerendersNSPName[] =
+    "Enable NoStatePrefetch on Navigation Predictor Isolated Prerenders";
+const char kEnableSRPIsolatedPrerendersNSPDescription[] =
+    "Enables NoStatePrefetch on Isolated Prerenders.";
+
 const char kDownloadAutoResumptionNativeName[] =
     "Enable download auto-resumption in native";
 const char kDownloadAutoResumptionNativeDescription[] =

chrome/browser/flag_descriptions.h

@@ -524,6 +524,9 @@ extern const char kEnableSRPIsolatedPrerendersDescription[];
 extern const char kEnableSRPIsolatedPrerenderProbingName[];
 extern const char kEnableSRPIsolatedPrerenderProbingDescription[];
 
+extern const char kEnableSRPIsolatedPrerendersNSPName[];
+extern const char kEnableSRPIsolatedPrerendersNSPDescription[];
+
 extern const char kEnableResamplingInputEventsName[];
 extern const char kEnableResamplingInputEventsDescription[];
 extern const char kEnableResamplingScrollEventsName[];

chrome/browser/prerender/isolated/isolated_prerender_params.cc

@@ -13,15 +13,18 @@
 #include "chrome/common/chrome_features.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
 
+const char kIsolatedPrerenderEnableNSPCmdLineFlag[] =
+    "isolated-prerender-nsp-enabled";
+
 bool IsolatedPrerenderIsEnabled() {
   return base::FeatureList::IsEnabled(features::kIsolatePrerenders);
 }
 
 bool IsolatedPrerenderNoStatePrefetchSubresources() {
-  // This is just a command line flag during development.
-  // TODO(robertogden): Move this to a experiment param when code complete.
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      "isolated-prerender-nsp-enabled");
+             kIsolatedPrerenderEnableNSPCmdLineFlag) ||
+         base::GetFieldTrialParamByFeatureAsBool(features::kIsolatePrerenders,
+                                                 "do_no_state_prefetch", false);
 }
 
 base::Optional<size_t> IsolatedPrerenderMaximumNumberOfPrefetches() {

chrome/browser/prerender/isolated/isolated_prerender_params.h

@@ -11,6 +11,9 @@
 #include "base/time/time.h"
 #include "url/gurl.h"
 
+// This command line flag enables NoStatePrefetch on Isolated Prerenders.
+extern const char kIsolatedPrerenderEnableNSPCmdLineFlag[];
+
 // Returns true if the Isolated Prerender feature is enabled.
 bool IsolatedPrerenderIsEnabled();
 

tools/metrics/histograms/enums.xml

@@ -40905,6 +40905,7 @@ from previous Chrome versions.
   <int value="-281844827" label="AutofillCreditCardAblationExperiment:enabled"/>
   <int value="-279920685" label="affiliation-based-matching:enabled"/>
   <int value="-279493876" label="WebVRExperimentalRendering:enabled"/>
+  <int value="-279208712" label="isolated-prerender-nsp-enabled"/>
   <int value="-278347667" label="default-tile-height"/>
   <int value="-277144896" label="enable-viewport-meta"/>
   <int value="-277118813" label="InterestFeedNotifications:disabled"/>