Repository: flutter
Issue: TextFormField + isDense + prefixIcon = unaligned text
Labels: a: text input,framework,f: material design,a: quality,has reproducible steps,P3,found in release: 2.5,found in release: 2.6,team-text-input,triaged-text-input

```dart
isDense: true,
prefixIcon: Icon(Icons.settings)
```
![image](https://user-images.githubusercontent.com/351125/64902241-0634f980-d67a-11e9-8614-803dc1a6154b.png)

```dart
isDense: true,
prefix: Icon(Icons.settings)
```
![image](https://user-images.githubusercontent.com/351125/64902238-fe755500-d679-11e9-9aeb-a72f0258c5be.png)


```dart
isDense: true,
prefix: Icon(Icons.settings, size: 16)
```
![image](https://user-images.githubusercontent.com/351125/64902245-18169c80-d67a-11e9-9cae-b5071cf9d626.png)


Full code: 
```dart
TextFormField(
            initialValue: "123456",
            decoration: InputDecoration(
              filled: true,
              isDense: true,
              prefix: Icon(Icons.settings, size: 16,),
            ),

```

```
➜ flutter doctor -v
[✓] Flutter (Channel dev, v1.10.1, on Mac OS X 10.14.6 18G95, locale en-BR)
    • Flutter version 1.10.1 at /usr/local/Cellar/flutter/dev
    • Framework revision ce45c2d3e6 (6 days ago), 2019-09-06 20:11:41 -0400
    • Engine revision b9ce2500d9
    • Dart version 2.5.0 (build 2.5.0-dev.4.0 be66176534)


[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/bernardoferrari/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling
      support)
    • Platform android-29, build-tools 29.0.2
    • Java binary at: /Users/bernardoferrari/Library/Application
      Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.5791312/Android
      Studio 3.5 Preview.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build
      1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.3, Build version 10G8
    • CocoaPods version 1.7.3

[✓] Android Studio (version 3.5)
    • Android Studio at /Users/bernardoferrari/Library/Application
      Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/191.5791312/Android
      Studio 3.5 Preview.app/Contents
    • Flutter plugin version 39.0.3
    • Dart plugin version 191.8423
    • Java version OpenJDK Runtime Environment (build
      1.8.0_202-release-1483-b49-5587405)

[✓] Android Studio
    • Android Studio at /Users/bernardoferrari/Library/Application
      Support/JetBrains/Toolbox/apps/AndroidStudio/ch-1/192.5863777/Android
      Studio 3.6 Preview.app/Contents
    • Flutter plugin version 39.0.4
    • Dart plugin version 192.6527
    • Java version OpenJDK Runtime Environment (build
      1.8.0_212-release-1586-b4-5784211)

[✓] IntelliJ IDEA Ultimate Edition (version 2019.2.2)
    • IntelliJ at /Users/bernardoferrari/Applications/JetBrains Toolbox/IntelliJ
      IDEA Ultimate.app
    • Flutter plugin version 38.2.4
    • Dart plugin version 192.6459

[✓] VS Code (version 1.38.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.4.1

[✓] Connected device (1 available)
    • Android SDK built for x86 64 • emulator-5554 • android-x64 • Android 10
      (API 29) (emulator)

• No issues found!
```