You can achieve that with:
settings.setUseWideViewPort(true);
But you should read more about it in Android SDK Documentation:
public synchronized void setUseWideViewPort (boolean use)
Added in API level 1 Sets whether the WebView should enable support
for the "viewport" HTML meta tag or should use a wide viewport.
When
the value of the setting is false, the layout width is always set to
the width of the WebView control in device-independent (CSS) pixels.
When the value is true and the page contains the viewport meta tag,
the value of the width specified in the tag is used. If the page does
not contain the tag or does not provide a width, then a wide viewport
will be used.
Parameters
use whether to enable support for the viewport meta tag
More info @
http://developer.android.com/reference/android/webkit/WebSettings.html#setUseWideViewPort(boolean)