Add chrome://flags entry to select overlay strategies

This patch adds a multi-value entry in about://flags that will
help enabling/disabling HW overlay strategies used to promote quads
to HW overlays.

Bug: 854677
Change-Id: Ibaedb02084a0b6aea490637bd6c4456caa63e29d
Reviewed-on: https://chromium-review.googlesource.com/1108520
Commit-Queue: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569403}

chrome/browser/about_flags.cc

@@ -228,6 +228,19 @@ const FeatureEntry::Choice kPullToRefreshChoices[] = {
 
 #endif  // USE_AURA
 
+const FeatureEntry::Choice kOverlayStrategiesChoices[] = {
+    {flag_descriptions::kOverlayStrategiesDefault, "", ""},
+    {flag_descriptions::kOverlayStrategiesNone,
+     switches::kEnableHardwareOverlays, ""},
+    {flag_descriptions::kOverlayStrategiesUnoccludedFullscreen,
+     switches::kEnableHardwareOverlays, "single-fullscreen"},
+    {flag_descriptions::kOverlayStrategiesUnoccluded,
+     switches::kEnableHardwareOverlays, "single-fullscreen,single-on-top"},
+    {flag_descriptions::kOverlayStrategiesOccludedAndUnoccluded,
+     switches::kEnableHardwareOverlays,
+     "single-fullscreen,single-on-top,underlay"},
+};
+
 const FeatureEntry::Choice kTouchTextSelectionStrategyChoices[] = {
     {flags_ui::kGenericExperimentChoiceDefault, "", ""},
     {flag_descriptions::kTouchSelectionStrategyCharacter,
@@ -1156,6 +1169,9 @@ const FeatureEntry kFeatureEntries[] = {
     {"composited-layer-borders", flag_descriptions::kCompositedLayerBordersName,
      flag_descriptions::kCompositedLayerBordersDescription, kOsAll,
      SINGLE_VALUE_TYPE(cc::switches::kShowCompositedLayerBorders)},
+    {"overlay-strategies", flag_descriptions::kOverlayStrategiesName,
+     flag_descriptions::kOverlayStrategiesDescription, kOsAll,
+     MULTI_VALUE_TYPE(kOverlayStrategiesChoices)},
     {"tint-gl-composited-content",
      flag_descriptions::kTintGlCompositedContentName,
      flag_descriptions::kTintGlCompositedContentDescription, kOsAll,

chrome/browser/flag_descriptions.cc

@@ -1231,6 +1231,19 @@ const char kOverlayScrollbarsFlashWhenMouseEnterDescription[] =
     "Flash Overlay Scrollbars When Mouse Enter a scrollable area. You must also"
     " enable Overlay Scrollbars.";
 
+const char kOverlayStrategiesName[] = "Select HW overlay strategies";
+const char kOverlayStrategiesDescription[] =
+    "Select strategies used to promote quads to HW overlays.";
+const char kOverlayStrategiesDefault[] = "Default";
+const char kOverlayStrategiesNone[] = "None";
+const char kOverlayStrategiesUnoccludedFullscreen[] =
+    "Unoccluded fullscreen buffers (single-fullscreen)";
+const char kOverlayStrategiesUnoccluded[] =
+    "Unoccluded buffers (single-fullscreen,single-on-top)";
+const char kOverlayStrategiesOccludedAndUnoccluded[] =
+    "Occluded and unoccluded buffers "
+    "(single-fullscreen,single-on-top,underlay)";
+
 const char kUseNewAcceptLanguageHeaderName[] = "Use new Accept-Language header";
 const char kUseNewAcceptLanguageHeaderDescription[] =
     "Adds the base language code after other corresponding language+region "

chrome/browser/flag_descriptions.h

@@ -766,6 +766,14 @@ extern const char kOverlayScrollbarsFlashAfterAnyScrollUpdateDescription[];
 extern const char kOverlayScrollbarsFlashWhenMouseEnterName[];
 extern const char kOverlayScrollbarsFlashWhenMouseEnterDescription[];
 
+extern const char kOverlayStrategiesName[];
+extern const char kOverlayStrategiesDescription[];
+extern const char kOverlayStrategiesDefault[];
+extern const char kOverlayStrategiesNone[];
+extern const char kOverlayStrategiesUnoccludedFullscreen[];
+extern const char kOverlayStrategiesUnoccluded[];
+extern const char kOverlayStrategiesOccludedAndUnoccluded[];
+
 extern const char kUseNewAcceptLanguageHeaderName[];
 extern const char kUseNewAcceptLanguageHeaderDescription[];
 

tools/metrics/histograms/enums.xml

@@ -27843,6 +27843,7 @@ from previous Chrome versions.
   <int value="-45067971" label="NewPrintPreview:disabled"/>
   <int value="-40935502" label="ContextualSuggestionsSlimPeekUI:enabled"/>
   <int value="-35388407" label="AshNewSystemMenu:disabled"/>
+  <int value="-30966385" label="enable-hardware-overlays"/>
   <int value="-29847483" label="MemoryAblation:enabled"/>
   <int value="-23804418"
       label="NTPArticleSuggestionsExpandableHeader:disabled"/>