Expose custom tab client gyp target in chromium

A custom tab client project has been mirrored in third_party. We
should add a gyp target to compile it in upstream, and delete the
downstream one.

This CL also updated java.gypi to let it take customizable
src suffix, just like java_apk.gypi.

BUG=NONE

Review URL: https://codereview.chromium.org/1222403005

Cr-Original-Commit-Position: refs/heads/master@{#338399}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 059d5d826a3803cdb4a18f217503bf6860463b3b

all.gyp

@@ -887,6 +887,7 @@
                 '../chrome/chrome.gyp:chrome_shell_uiautomator_tests',
                 '../chrome/chrome.gyp:chromedriver_webview_shell_apk',
                 '../chrome/chrome.gyp:unit_tests_apk',
+                '../third_party/custom_tabs_client/src/custom_tabs_client.gyp:custom_tabs_client_example_apk',
               ],
             }],
           ],

java.gypi

@@ -79,6 +79,7 @@
     'never_lint%': 0,
     'findbugs_stamp': '<(intermediate_dir)/findbugs.stamp',
     'run_findbugs%': 0,
+    'java_in_dir_suffix%': '/src',
     'proguard_config%': '',
     'proguard_preprocess%': '0',
     'enable_errorprone%': '0',
@@ -259,7 +260,7 @@
       'variables': {
         'extra_args': [],
         'extra_inputs': [],
-        'java_sources': ['>!@(find >(java_in_dir)/src >(additional_src_dirs) -name "*.java")'],
+        'java_sources': ['>!@(find >(java_in_dir)>(java_in_dir_suffix) >(additional_src_dirs) -name "*.java")'],
         'conditions': [
           ['enable_errorprone == 1', {
             'extra_inputs': [
@@ -315,7 +316,7 @@
     {
       'variables': {
         'src_dirs': [
-          '<(java_in_dir)/src',
+          '<(java_in_dir)<(java_in_dir_suffix)',
           '>@(additional_src_dirs)',
         ],
         'stamp_path': '<(lint_stamp)',