doc: add quickstart to linux and macos

also, better install_deps

NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=1112663002

Review URL: https://codereview.chromium.org/1112663002

3 files changed, 94 insertions, 12 deletions

diff --git a/site/user/quick/linux.md b/site/user/quick/linux.md
index ef4f95b667..7a172a5d95 100644
--- a/site/user/quick/linux.md
+++ b/site/user/quick/linux.md
@@ -1,6 +1,42 @@
 Linux
 =====
 
+Quickstart
+----------
+
+1.  Install depot tools.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
+        export PATH="${PWD}/depot_tools:${PATH}"
+
+2.  Get Skia.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://skia.googlesource.com/skia'
+        cd skia
+
+3.  Install Dependencies (may require sudo).
+
+    <!--?prettify lang=sh?-->
+
+        tools/install_dependencies.sh
+
+4.  Build.
+
+    <!--?prettify lang=sh?-->
+
+        bin/sync-and-gyp && ninja -C out/Debug
+
+5.  Run DM (the Skia test app) and SampleApp.
+
+    <!--?prettify lang=sh?-->
+
+        out/Debug/dm
+        out/Debug/SampleApp
+
 Prerequisites
 -------------
 
diff --git a/site/user/quick/macos.md b/site/user/quick/macos.md
index ed74551d8b..c9d09a3bf1 100644
--- a/site/user/quick/macos.md
+++ b/site/user/quick/macos.md
@@ -1,6 +1,38 @@
 Mac OS X
 ========
 
+Quickstart
+----------
+
+1.  Install [XCode](http://developer.apple.com/xcode/).
+
+2.  Install depot tools.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
+        export PATH="${PWD}/depot_tools:${PATH}"
+
+3.  Get Skia.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://skia.googlesource.com/skia'
+        cd skia
+
+4.  Build.
+
+    <!--?prettify lang=sh?-->
+
+        bin/sync-and-gyp && ninja -C out/Debug
+
+5.  Run DM (the Skia test app) and SampleApp.
+
+    <!--?prettify lang=sh?-->
+
+        out/Debug/dm
+        open out/Debug/SampleApp.app
+
 Prerequisites
 -------------
 
diff --git a/tools/install_dependencies.sh b/tools/install_dependencies.sh
index ae98884d1e..037b8940bd 100755
--- a/tools/install_dependencies.sh
+++ b/tools/install_dependencies.sh
@@ -10,21 +10,35 @@
 
 set -e
 
+# Return 0 iff all package name arguments are installed.
+dpkg_all_installed() {
+    for arg; do
+        if !(dpkg-query -W -f'${Status}' "$arg" 2>/dev/null | \
+            grep -q "ok installed"); then
+            return 1
+        fi
+    done
+    return 0
+}
+
 if command -v lsb_release > /dev/null ; then
     case $(lsb_release -i -s) in
         Ubuntu)
-            sudo apt-get install \
-                build-essential \
-		libfreetype6-dev \
-		libfontconfig-dev \
-		libpng12-dev \
-		libgif-dev \
-		libqt4-dev \
-		clang
-	    if [ $(lsb_release -r -s) = '14.04' ] ; then
-		sudo apt-get install \
-		    ninja-build
-	    fi
+            PACKAGES=$(cat<<-EOF
+		build-essential
+		libfreetype6-dev
+		libfontconfig-dev
+		libpng12-dev
+		libgif-dev
+		libqt4-dev
+		EOF
+            )
+           if [ $(lsb_release -r -s) = '14.04' ] ; then
+               PACKAGES="${PACKAGES} ninja-build"
+            fi
+            if ! dpkg_all_installed $PACKAGES; then
+                sudo apt-get install $PACKAGES
+            fi
             exit
             ;;
     esac