[Android] Update java_files build docs

Use of java_files is being deprecated in favor of sources.
Update documentation that still references java_files.

TBR=aluo,bialpio,dpranke,pasko

Bug: 1035082
Change-Id: Ibcab73a9d90e010cdffd3018d3fd238662945f97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980981Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
Commit-Queue: Natalie Chouinard <chouinard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727284}

base/android/jni_generator/sample_for_tests.h

@@ -50,7 +50,7 @@ namespace android {
 //      ]
 //    }
 //    android_library("java") {
-//      java_files = [
+//      sources = [
 //        "java/src/org/chromium/example/jni_generator/SampleForTests.java",
 //        "java/src/org/chromium/example/jni_generator/NonJniFile.java",
 //      ]

chrome/android/javatests/src/org/chromium/chrome/browser/vr/adding_new_tests.md

@@ -169,9 +169,9 @@ parameterized class. The general things you will need to are:
 ### Add The New File
 
 Add the new test class to [`//chrome/android/BUILD.gn`][build_gn]. If it is a VR
-test class, it should be added to the `java_files` list of the
+test class, it should be added to the `sources` list of the
 `chrome_test_vr_java` `android_library` target. If it is an AR test class, it
-should be added to the `java_files` list of the `chrome_test_ar_java`
+should be added to the `sources` list of the `chrome_test_ar_java`
 `android_library` target.
 
 ## AR Playback Datasets

chrome/test/android/javatests/src/org/chromium/chrome/test/pagecontroller/README.md

@@ -36,7 +36,7 @@ git checkout -b pagecontroller_codelab
 ...
 android_library("chrome_java_test_pagecontroller") {
   testonly = true
-  java_files = [
+  sources = [
   ...
     "javatests/src/org/chromium/chrome/test/pagecontroller/controllers/android/PermissionDialog.java",
 +   "javatests/src/org/chromium/chrome/test/pagecontroller/controllers/codelab/SearchEngineSelectionControllerForCodelab.java",

chrome/test/android/javatests/src/org/chromium/chrome/test/pagecontroller/codelabsolution/README.md

@@ -256,7 +256,7 @@ public class ChromeMenu extends PageController {
 ```
 android_library("chrome_java_test_pagecontroller") {
   testonly = true
-  java_files = [
+  sources = [
 ...
     "javatests/src/org/chromium/chrome/test/pagecontroller/controllers/android/PermissionDialog.java",
 +    "javatests/src/org/chromium/chrome/test/pagecontroller/controllers/codelab/SettingsControllerForCodelab.java",

docs/android_dynamic_feature_modules.md

@@ -242,7 +242,7 @@ import("//chrome/android/features/foo/public/foo_public_java_sources.gni")
 ...
 android_library("chrome_java") {
   ...
-  java_files += foo_public_java_sources
+  sources += foo_public_java_sources
 }
 ...
 ```
@@ -256,7 +256,7 @@ import("//build/config/android/rules.gni")
 
 android_library("java") {
   # Define like ordinary Java Android library.
-  java_files = [
+  sources = [
     "java/src/org/chromium/chrome/features/foo/FooImpl.java",
     # Add other Java classes that should go into the Foo DFM here.
   ]

testing/android/docs/components_for_testing.md

@@ -117,7 +117,7 @@ target.
 
 ``` python
 android_library("my_test_service") {
-  java_files = [ "src/org/chromium/chrome/test/MyTestService.java" ]
+  sources = [ "src/org/chromium/chrome/test/MyTestService.java" ]
   deps = [ ... ]
 }
 ```

testing/android/docs/junit.md

@@ -108,8 +108,9 @@ public class MyRobolectricJUnitTest {
 ```python
 junit_binary("my_robolectric_tests") {
 
-    java_files = [
+    sources = [
         "java/src/foo/bar/MyJUnitTest.java"
+    ]
 
     deps = [
         "//my/test:dependency",