Move screenshot capture to Java-side.

base/test/android/javatests/src/org/chromium/base/test/ScreenshotOnFailureStatement.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.base.test;
+
+import android.support.test.InstrumentationRegistry;
+import android.support.test.uiautomator.UiDevice;
+
+import org.junit.runners.model.Statement;
+
+import org.chromium.base.CommandLine;
+import org.chromium.base.Log;
+import org.chromium.base.test.util.UrlUtils;
+
+import java.io.File;
+
+/**
+ * Statement that captures screenshots if |base| statement fails.
+ *
+ * If --screenshot-dir commandline flag is given, this statement
+ * will save a screenshot named failure.png to
+ * |UrlUtils.getIsolatedTestFilePath| under the subdirectory specified
+ * in the case of a test failure.
+ */
+public class ScreenshotOnFailureStatement extends Statement {
+    private static final String TAG = "ScreenshotOnFail";
+
+    private static final String SCREENSHOT_FILENAME = "failure.png";
+
+    private final Statement mBase;
+
+    public ScreenshotOnFailureStatement(final Statement base) {
+        mBase = base;
+    }
+
+    @Override
+    public void evaluate() throws Throwable {
+        try {
+            mBase.evaluate();
+        } catch (Throwable e) {
+            String subdir = CommandLine.isInitialized()

[jbudorick, 2017/05/05 01:21:58]

This may be more readable/cleaner if you split the screenshot capture logic into
a new function, have it return early in the failure conditions, and then just
have this catch block be

  } catch (Throwable e) {
      takeScreenshot();
      throw e;
  }

[mikecase (-- gone --), 2017/05/05 18:09:19]

Done

+                    ? CommandLine.getInstance().getSwitchValue("screenshot-dir")
+                    : null;
+            if (subdir == null) {
+                Log.d(TAG,
+                        "Did not save screenshot of failure. Must specify --screenshot-dir "
+                                + "command-line flag to enable this feature.");
+                throw e;
+            }
+
+            UiDevice uiDevice = UiDevice.getInstance(InstrumentationRegistry.getInstrumentation());

[jbudorick, 2017/05/05 01:21:58]

I assume this was the only way to do this?

[mikecase (-- gone --), 2017/05/05 18:09:19]

I looked at basically every other option. So there is some PixelCopy class used
elsewhere...
https://developer.android.com/reference/android/view/PixelCopy.html

but you need an Activity context as far as I know to use it. Also only available
in higher SDK levels.

Basically it seems like UiAutomator has extra priviledges in Android framework,
so its able to screencap when/where most things could not.
I did not want to use UiAutomator here...but it seems like best way.

+            File path = new File(UrlUtils.getIsolatedTestFilePath(subdir));

[jbudorick, 2017/05/05 01:21:58]

While I'm ok with using the isolated test file path for now, I'd like to
eventually switch the test output directory to something other than what we use
for the test input directory. To do so, we should create a function that
introduces some indirection here -- calling it, which then calls
UrlUtils.getIsolatedTestFilePath.

[mikecase (-- gone --), 2017/05/05 18:09:19]

Added UrlUtils.getTestFileOutputPath

+            if (!path.exists()) {
+                if (!path.mkdirs()) {
+                    Log.d(TAG, String.format("Failed to create %s. Can't save screenshot.", path));
+                    throw e;
+                }
+            }
+            File file = new File(path + "/" + SCREENSHOT_FILENAME);
+            Log.d(TAG, String.format("Saving screenshot of test failure, %s", file));
+            uiDevice.takeScreenshot(file);
+            throw e;
+        }
+    }
+}