8. A method, comprising: at an electronic device with a display and a touch-sensitive surface: concurrently displaying on the display a first text entry area, and an integrated input area, the integrated input area including: a left portion with a left side of a split keyboard with a first set of characters; a right portion with a right side of the split keyboard with a second set of characters; and a center portion in between the left portion and the right portion; detecting a first input on the touch-sensitive surface; in response to detecting the first input, entering a reconfiguration mode for the integrated input area; and, while in the reconfiguration mode for the integrated input area: detecting a second input by a first thumb and/or a second thumb; in response to detecting the second input, adjusting the size of at least one of the left side and the right side of the split keyboard in the integrated input area, maintaining the first set of characters in the left side of the split keyboard, and maintaining the second set of characters in the right side of the split keyboard; detecting a third input; and, in response to detecting the third input, exiting the reconfiguration mode for the integrated input area.
13. The method of claim 8 , wherein the second input includes a horizontal movement of the first thumb towards a vertical side of the display closest to the first thumb; and the method includes: in response to detecting the horizontal movement of the first thumb towards the vertical side of the display closest to the first thumb, reducing the size of the left side and the right side of the split keyboard.