Use compileOnly dependency (#294)

Summary:
Fixes #293.
Pull Request resolved: https://github.com/facebook/flipper/pull/294

Reviewed By: danielbuechele

Differential Revision: D10367678

Pulled By: passy

fbshipit-source-id: 69ccdc470b20d5d43e1bb3c1eb4e52c2e01debb5

android/build.gradle

@@ -53,7 +53,7 @@ android {
         implementation deps.lithoCore
         implementation deps.lithoWidget
         implementation deps.rhino
-        implementation deps.leakcanary
+        compileOnly deps.leakcanary
 
         testImplementation deps.mockito
         testImplementation deps.robolectric

docs/leak-canary-plugin.md

@@ -9,6 +9,16 @@ The LeakCanary plugin provides developers with Flipper support for [LeakCanary](
 
 Note: this plugin is only available for Android.
 
+Ensure that you already have an explicit dependency in your application's
+`build.gradle`, e.g.
+
+```groovy
+dependencies {
+  debugImplementation 'com.squareup.leakcanary:leakcanary-android:1.6.1'
+  releaseImplementation 'com.squareup.leakcanary:leakcanary-android-no-op:1.6.1'
+}
+```
+
 ### Android
 
 First, add the plugin to your Flipper client instance: