Blob: Cap DataPipes at 2MB by default.

This CL increases the blob DataPipe cap from 512kb to 2MB to improve
performance.

Trials show a 12% progression at P95 when reading the body from a
cache_storage response provided to a subresource service worker
FetchEvent.  A partner site showed a 5% progression at P95 in core
css stylesheet load times.

Bug: 1010199
Change-Id: I040cadc1d6d7c081b242f72ad286a2f942b0a53f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1859839Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710783}

content/browser/service_worker/service_worker_installed_scripts_sender_unittest.cc

@@ -350,7 +350,7 @@ TEST_F(ServiceWorkerInstalledScriptsSenderTest, FailedToSendBody) {
 TEST_F(ServiceWorkerInstalledScriptsSenderTest, FailedToSendMetaData) {
   const GURL kMainScriptURL = version()->script_url();
   std::string long_meta_data = "I'm the meta data!";
-  long_meta_data.resize(1E6, '!');
+  long_meta_data.resize(3E6, '!');
   std::map<GURL, ExpectedScriptInfo> kExpectedScriptInfoMap = {
       {kMainScriptURL,
        {1,

testing/variations/fieldtrial_testing_config.json

@@ -1345,28 +1345,6 @@
             ]
         }
     ],
-    "BlobDataPipeTuning": [
-        {
-            "platforms": [
-                "android",
-                "chromeos",
-                "linux",
-                "mac",
-                "windows"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled_2MB_v1",
-                    "params": {
-                        "capacity_bytes": "2097152"
-                    },
-                    "enable_features": [
-                        "BlobDataPipeTuning"
-                    ]
-                }
-            ]
-        }
-    ],
     "BlockPromptsIfIgnoredOften": [
         {
             "platforms": [

third_party/blink/common/blob/blob_utils.cc

@@ -21,7 +21,9 @@ const base::Feature kBlobDataPipeTuningFeature{
     "BlobDataPipeTuning", base::FEATURE_DISABLED_BY_DEFAULT};
 
 constexpr int kBlobMinDataPipeCapacity = 1024;
-constexpr int kBlobDefaultDataPipeCapacity = 512 * 1024;
+
+// The 2MB limit was selected via a finch trial.
+constexpr int kBlobDefaultDataPipeCapacity = 2 * 1024 * 1024;
 
 constexpr base::FeatureParam<int> kBlobDataPipeCapacity{
     &kBlobDataPipeTuningFeature, "capacity_bytes",