Make incognito quota dynamic.

The hard limit for incognito quota is removed and the quota is
dynamically set based on a Finch controllable ratio of the amount of
physical memory.

Bug: 1017120
Change-Id: I218295f661a9080b61bfd0e1487f58678e3bfe1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1878190
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Reviewed-by: Jarryd Goodman <jarrydg@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710710}

storage/browser/quota/quota_features.cc

@@ -30,5 +30,19 @@ const base::Feature kStaticHostQuota{"StaticHostQuota",
 // removing limits on how much disk space the temporary pool can consume.
 const base::Feature kQuotaUnlimitedPoolSize{"QuotaUnlimitedPoolSize",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
+
+// IncognitoDynamicQuota enables dynamic assignment of quota to incognito mode
+// based on the physical memory size and removes the fixed upper cap for it.
+const base::Feature kIncognitoDynamicQuota{"IncognitoDynamicQuota",
+                                           base::FEATURE_DISABLED_BY_DEFAULT};
+
+// Dynamic quota for incognito mode would be set by a random fraction of
+// physical memory, between |IncognitoQuotaRatioLowerBound| and
+// |IncognitoQuotaRatioUpperBound|.
+constexpr base::FeatureParam<double> kIncognitoQuotaRatioLowerBound{
+    &kIncognitoDynamicQuota, "IncognitoQuotaRatioLowerBound", 0.1};
+constexpr base::FeatureParam<double> kIncognitoQuotaRatioUpperBound{
+    &kIncognitoDynamicQuota, "IncognitoQuotaRatioUpperBound", 0.2};
+
 }  // namespace features
 }  // namespace storage

storage/browser/quota/quota_features.h

@@ -24,6 +24,11 @@ extern const base::Feature kStaticHostQuota;
 COMPONENT_EXPORT(STORAGE_BROWSER)
 extern const base::Feature kQuotaUnlimitedPoolSize;
 
+COMPONENT_EXPORT(STORAGE_BROWSER)
+extern const base::Feature kIncognitoDynamicQuota;
+extern const base::FeatureParam<double> kIncognitoQuotaRatioLowerBound;
+extern const base::FeatureParam<double> kIncognitoQuotaRatioUpperBound;
+
 }  // namespace features
 
 }  // namespace storage

storage/browser/quota/quota_settings.cc

@@ -39,14 +39,24 @@ base::Optional<storage::QuotaSettings> CalculateNominalDynamicSettings(
   if (is_incognito) {
     // The incognito pool size is a fraction of the amount of system memory,
     // and the amount is capped to a hard limit.
-    const double kIncognitoPoolSizeRatio = 0.1;  // 10%
-    const int64_t kMaxIncognitoPoolSize = 300 * kMBytes;
+    double kIncognitoPoolSizeRatio = 0.1;  // 10%
+    int64_t kMaxIncognitoPoolSize = 300 * kMBytes;
+    if (base::FeatureList::IsEnabled(features::kIncognitoDynamicQuota)) {
+      const double lower_bound = features::kIncognitoQuotaRatioLowerBound.Get();
+      const double upper_bound = features::kIncognitoQuotaRatioUpperBound.Get();
+      kIncognitoPoolSizeRatio =
+          lower_bound + (base::RandDouble() * (upper_bound - lower_bound));
+      kMaxIncognitoPoolSize = std::numeric_limits<int64_t>::max();
+    } else {
+      kMaxIncognitoPoolSize =
+          RandomizeByPercent(kMaxIncognitoPoolSize, kRandomizedPercentage);
+    }
 
     storage::QuotaSettings settings;
-    settings.pool_size = std::min(
-        RandomizeByPercent(kMaxIncognitoPoolSize, kRandomizedPercentage),
-        static_cast<int64_t>(base::SysInfo::AmountOfPhysicalMemory() *
-                             kIncognitoPoolSizeRatio));
+    settings.pool_size =
+        std::min(kMaxIncognitoPoolSize,
+                 static_cast<int64_t>(base::SysInfo::AmountOfPhysicalMemory() *
+                                      kIncognitoPoolSizeRatio));
     settings.per_host_quota = settings.pool_size / 3;
     settings.session_only_per_host_quota = settings.per_host_quota;
     settings.refresh_interval = base::TimeDelta::Max();

testing/variations/fieldtrial_testing_config.json

@@ -2997,6 +2997,29 @@
             ]
         }
     ],
+    "IncognitoDynamicQuota": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "WideRange",
+                    "params": {
+                        "RatioLowerBound": "0.1",
+                        "RatioUpperBound": "0.2"
+                    },
+                    "enable_features": [
+                        "IncognitoDynamicQuota"
+                    ]
+                }
+            ]
+        }
+    ],
     "IncognitoWindowInProductHelp": [
         {
             "platforms": [