By default, the Google search bar should be 15 pixels high, as far as I can understand, by checking the Google Maps DOM with the search bar turned on.
This is what the search bar in the DOM looks like:
<div id=":0:formId" class="gels-form-div">
<img id=":0:logoId" class="gels-logo" src="http://www.google.com/uds/modules/elements/localsearch/logo_66x22.png">
<input id=":0:inputId" class="gels-input" type="text" name="search" title="search" value="search the map" style="width: 153px; ">
<input id=":0:buttonId" class="gels-button" type="submit" value="Search" title="search">
</div>
Make sure your application does not override class height gels-input. If this does not help, you can redefine the height yourself:
input.gels-input {
height: 15px;
}