Revert "Removing unnecessary dontwarns from cronet proguard configs"

This reverts commit 987d1fa4.

Reason for revert: Broke internal targets depending on cronet, that treat proguard warnings as errors

Original change's description:
> Removing unnecessary dontwarns from cronet proguard configs
> 
> Bug: 887942
> Change-Id: I120d6aa7681d7d86ce3ee9d2b8add7bd5dc0e0da
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804075
> Auto-Submit: Sam Maier <smaier@chromium.org>
> Commit-Queue: Ryan Hamilton <rch@chromium.org>
> Reviewed-by: Ryan Hamilton <rch@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#696870}

TBR=rch@chromium.org,smaier@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 887942
Change-Id: I58746c8ad28176c6115b5b2ec205bd372f3a7513
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1812133Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697842}

components/cronet/android/cronet_impl_native_proguard.cfg

@@ -5,6 +5,28 @@
     public <init>(android.content.Context);
 }
 
+# Suppress unnecessary warnings.
+-dontnote org.chromium.net.ProxyChangeListener$ProxyReceiver
+-dontnote org.chromium.net.AndroidKeyStore
+# Needs 'void setTextAppearance(int)' (API level 23).
+-dontwarn org.chromium.base.ApiCompatibilityUtils
+# Needs 'boolean onSearchRequested(android.view.SearchEvent)' (API level 23).
+-dontwarn org.chromium.base.WindowCallbackWrapper
+
+# Generated for chrome apk and not included into cronet.
+-dontwarn org.chromium.base.library_loader.NativeLibraries
+-dontwarn org.chromium.base.multidex.ChromiumMultiDexInstaller
+-dontwarn org.chromium.base.metrics.CachedMetrics
+-dontwarn org.chromium.base.library_loader.LibraryLoader
+-dontwarn org.chromium.base.SysUtils
+
+# Objects of this type are passed around by native code, but the class
+# is never used directly by native code. Since the class is not loaded, it does
+# not need to be preserved as an entry point.
+-dontnote org.chromium.net.UrlRequest$ResponseHeadersMap
+# https://android.googlesource.com/platform/sdk/+/marshmallow-mr1-release/files/proguard-android.txt#54
+-dontwarn android.support.**
+
 # This class should be explicitly kept to avoid failure if
 # class/merging/horizontal proguard optimization is enabled.
 -keep class org.chromium.base.CollectionUtil

components/cronet/android/test/proguard.cfg

 # Proguard configuration that is common for all type of tests.
 
 -keepattributes Signature,InnerClasses,SourceFile,LineNumberTable,EnclosingMethod
+-dontwarn io.netty.**
 -keep class io.netty.** { *; }
 # Keep ChromiumNativeTestSupport & ChromiumPlatformOnlyTestSupport since they are
 # instantiated through Reflection by the smoke tests.
 -keep class org.chromium.net.smoke.ChromiumNativeTestSupport
 -keep class org.chromium.net.smoke.ChromiumPlatformOnlyTestSupport
 
+# https://android.googlesource.com/platform/sdk/+/marshmallow-mr1-release/files/proguard-android.txt#54
+-dontwarn android.support.**
+
 # Do not obfuscate this class for testing since some of the tests check the class
 # name in order to check that an instantiated engine is the Java one.
 -keepnames class org.chromium.net.impl.JavaCronetEngine
@@ -20,3 +24,6 @@
 
 -keep class org.chromium.net.TestFilesInstaller
 -keep class org.chromium.net.MetricsTestUtil
+
+# Generated for chrome apk and not included into cronet.
+-dontwarn org.chromium.base.library_loader.NativeLibraries