OkHttp: Upgrade to 4.9.1 (minSdkVersion 21)

Until now, we have stuck with the 3.12 long-term branch so as
to keep support for older API levels. However, this means that
the version we're using is 2.5 years old at this point. The
3.12 branch will stop receiving critical updates in December
2021.

Since use of the OkHttp extension is optional anyway, it seems
preferable to move to a modern version of OkHttp at this point.

PiperOrigin-RevId: 381465269

RELEASENOTES.md

@@ -109,6 +109,9 @@
     *   Fix session description (SDP) parsing to use a HashMap-like behaviour
         for duplicated attributes.
         ([#9014](https://github.com/google/ExoPlayer/issues/9014)).
+*   OkHttp extension:
+    *   Switch to OkHttp 4.9.1. This increases the extension's minimum SDK
+        version requirement from 16 to 21.
 
 ### 2.14.1 (2021-06-11)
 

extensions/okhttp/build.gradle

@@ -13,6 +13,8 @@
 // limitations under the License.
 apply from: "$gradle.ext.exoplayerSettingsDir/common_library_config.gradle"
 
+android.defaultConfig.minSdkVersion 21
+
 dependencies {
     implementation project(modulePrefix + 'library-common')
     implementation 'androidx.annotation:annotation:' + androidxAnnotationVersion
@@ -21,11 +23,7 @@ dependencies {
     testImplementation project(modulePrefix + 'testutils')
     testImplementation 'com.squareup.okhttp3:mockwebserver:' + mockWebServerVersion
     testImplementation 'org.robolectric:robolectric:' + robolectricVersion
-    // Do not update to 3.13.X or later until minSdkVersion is increased to 21:
-    // https://cashapp.github.io/2019-02-05/okhttp-3-13-requires-android-5
-    // Since OkHttp is distributed as a jar rather than an aar, Gradle won't
-    // stop us from making this mistake!
-    api 'com.squareup.okhttp3:okhttp:3.12.11'
+    api 'com.squareup.okhttp3:okhttp:4.9.1'
 }
 
 ext {