Add Assistant Media Session support flag to about flags.

Bug: b/129715312
Test: Manual Test
Change-Id: I15bee4721a8133913fffa73f28ac53566005368e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1679057
Reviewed-by: Yue Li <updowndota@chromium.org>
Commit-Queue: Li Lin <llin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672704}

diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 9d328725..03fb39fa3 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc

@@ -3452,6 +3452,13 @@
      flag_descriptions::kEnableAssistantKeyRemappingName,
      flag_descriptions::kEnableAssistantKeyRemappingDescription, kOsCrOS,
      FEATURE_VALUE_TYPE(chromeos::assistant::features::kAssistantKeyRemapping)},
+
+    {"enable-assistant-media-session-integration",
+     flag_descriptions::kEnableAssistantMediaSessionIntegrationName,
+     flag_descriptions::kEnableAssistantMediaSessionIntegrationDescription,
+     kOsCrOS,
+     FEATURE_VALUE_TYPE(
+         chromeos::assistant::features::kEnableMediaSessionIntegration)},
 #endif  // defined(OS_CHROMEOS)
 
     {"click-to-call-receiver", flag_descriptions::kClickToCallReceiverName,

diff --git a/chrome/browser/flag-metadata.json b/chrome/browser/flag-metadata.json
index 7065bd11..f091650 100644
--- a/chrome/browser/flag-metadata.json
+++ b/chrome/browser/flag-metadata.json

@@ -801,6 +801,11 @@
     "expiry_milestone": 78
   },
   {
+    "name": "enable-assistant-media-session-integration",
+    "owners": [ "croissant-eng" ],
+    "expiry_milestone": 78
+  },
+  {
     "name": "enable-assistant-app-support",
     "owners": [ "croissant-eng" ],
     "expiry_milestone": 78

diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 91f8b86..adf695d 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc

@@ -3064,6 +3064,11 @@
     "Combine Launcher search with the power of Assistant to provide the most "
     "useful answer for each query. Requires Assistant to be enabled.";
 
+const char kEnableAssistantMediaSessionIntegrationName[] =
+    "Assistant Media Session integration";
+const char kEnableAssistantMediaSessionIntegrationDescription[] =
+    "Enable Assistant Media Session Integration.";
+
 const char kEnableAssistantVoiceMatchName[] = "Enable Assistant Voice Match";
 const char kEnableAssistantVoiceMatchDescription[] =
     "Enable the Assistant Voice Match feature";

diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 2fd0fda..66eb21f 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h

@@ -1827,6 +1827,9 @@
 extern const char kEnableAssistantLauncherIntegrationName[];
 extern const char kEnableAssistantLauncherIntegrationDescription[];
 
+extern const char kEnableAssistantMediaSessionIntegrationName[];
+extern const char kEnableAssistantMediaSessionIntegrationDescription[];
+
 extern const char kEnableAssistantVoiceMatchName[];
 extern const char kEnableAssistantVoiceMatchDescription[];
 

diff --git a/tools/metrics/histograms/enums.xml b/tools/metrics/histograms/enums.xml
index d3f14d5..1114de7 100644
--- a/tools/metrics/histograms/enums.xml
+++ b/tools/metrics/histograms/enums.xml

@@ -34426,6 +34426,8 @@
   <int value="-757282194" label="EnableFilesystemInIncognito:enabled"/>
   <int value="-750175757" label="ClientLoFi:enabled"/>
   <int value="-749048160" label="enable-panels"/>
+  <int value="-748571227"
+      label="AssistantEnableMediaSessionIntegration:enabled"/>
   <int value="-747463111" label="ContentSuggestionsNotifications:disabled"/>
   <int value="-746328467" label="ExpensiveBackgroundTimerThrottling:disabled"/>
   <int value="-744159181" label="disable-spdy-proxy-dev-auth-origin"/>
@@ -36112,6 +36114,8 @@
   <int value="1785093465" label="enable-document-passive-event-listeners"/>
   <int value="1786229999" label="disable-md-downloads"/>
   <int value="1786386775" label="TranslateCompactUI:disabled"/>
+  <int value="1786692012"
+      label="AssistantEnableMediaSessionIntegration:disabled"/>
   <int value="1789517771" label="MacV2Sandbox:enabled"/>
   <int value="1789793147" label="HTTPSServerPreviewsUsingURLLoader:disabled"/>
   <int value="1792609232" label="NTPShortcuts:enabled"/>